“In a Mirror Brightly”: French Attempts to Build Reflecting Telescopes Using Platinum

The most explicit and detailed of the arguments of this common type is the recent doctoral dissertation of Pav Anton Peter , “Eighteenth-century optics: The age of unenlightenment” (Indiana University, 1964). Cf. the more cautious treatment in Ronchi Vasco , Histoire de la lumière (trans. from the Italian by Juliette Taton, Paris, 1956), ch. 6. The most detailed of the general treatments of optics in the eighteenth century is that by Fortia and Lalande in the 2nd edition of Montucla's J. F. Histoire des mathématiques … , iii (Achevé et publié par Jérôme de La Lande, Paris, 1802), 427–605.

Bouguer Pierre , Optical treatise on the gradation of light (trans., with Introduction and Notes, by Middleton Knowles W. E. , Toronto, 1961). The brief analysis of his contribution in Charles Fabry's “Physique” section of the first volume of Histoire des sciences en France, which appeared as vol. xiv of Histoire de la nation française (15 vols, ed. by Hanotaux Gabriel , Paris, 1924), sets Bouguer in exactly the context used here.

This was based, of course, upon Newton's belief in the proportionality of dispersion and refraction. Euler was led to reject this through his erroneous supposition of the achromatism of the eye. On the question of Newton's own opinion of the possibility of achromatic lenses, see Whiteside D. T. , The mathematical papers of Isaac Newton, iii (Cambridge, 1969), Part III, esp. pp. 442–3 and 468.

Although he rejected Euler's position in 1752–3, his continuing work resulted in the achromatic refractor by 1758. For a brief biography of Dollond, with all of his relevant papers appended, see Kelly John , The life of John Dollond, F.R.S., inventor of the achromatic telescope (London, 1808). I have ignored the thorny question of Dollond's knowledge of prior work along these lines, for which see the indications in King Henry C. , The history of the telescope (London, 1955), 144–5, 154–5.

On the English developments from Newton to Herschel, see ch. 5 in King. On Herschel's telescopes, King's ch. 7 may be usefully supplemented by Dreyer's J. L. E. “Introduction” to The scientific papers of Sir William Herschel (2 vols, London, 1912), esp. pp. xxiv–xxviii, xlv–lvi, and by the M.Sc. thesis of Moss C. T. , “The telescopes of Sir William Herschel” (University of London, 1949).

For an analysis of various reasons, social as well as technical, for the French lag, see Daumas Maurice , Les instruments scientifiques aux XVII^e et XVIII^e siècles (Paris, 1953), 123–43. The only really comparable French worker in mid-century was C. S. Passemant, on whom see in ibid., esp. pp. 347–9.

The major printed sources on this development are Cassini J. D. , Mémoires pour servir à l'histoire des sciences et à celle de l'Observatoire royal de Paris (Paris, 1810) and Wolf Charles , Histoire de l'Observatoire de Paris de sa fondation à 1793 (Paris, 1902).

Cassini , Mémoires…, 15.

In addition to the materials on this creation in ibid. (86–94, 217–23) and in Daumas's Instruments (135–7), the latter dedicated a separate article to it: “Le corps des ingénieurs brevetés en instruments scientifiques (1787)”, Actes du VI^e Congrès international d'histoire des sciences, ii (Paris, 1953), 478–88.

As with Daumas's general and specific treatment of the ‘corps’, Guillaume Bigourdan, though briefly analysing this establishment in his Histoire de l'astronomie d'observation et des observatoires en France , Seconde Partie (Paris, 1930), 148–55, dealt with it at greater length separately: “Un Institut d'optique à Paris, au XVIII^e siècle”, Comptes rendus du Congrès des Sociétés savantes en 1921, Sciences, Deuxième Partie (Notes et Mémoires), 19–74.

Noël having been removed in 1774, his position was split, in the next year, with the creation of a curator of instruments in physics—which was awarded to J. B. Leroy—and a curator of optical instruments—given to Rochon. On the latter, see Delambre J. B. J. , “Notice sur la vie et les ouvrages de M. Rochon”, Mémoires de l'Académie des sciences de l'Institut de France , 2^e série, ii (Paris, 1819), lxxiii–lxxxii, Lacroix Alfred , Figures de savants (4 vols, Paris, 1932–1938), iv, 15–24, and the good article by Dezas de la Roquette in Biographie universelle ( Michaud J. F. , ed., 45 vols, Paris, 1843–1858), 258–63.

Although several of these works were reported to the Académie des sciences (of which Rochon became a resident member in 1771) between 1774 and 1776 and duly printed in its Mémoires, Rochon reissued them, along with others—most notably those dealing with the perfection of his most significant instrument, the prismatic micrometer, and the priority struggle that it engaged him in with Boscovich and Maskelyne—in his Recueil de mémoires sur la mécanique et la physique (Paris, 1783). The quotation comparing his achromatic refractor's effect to that of Dollond's instrument may be found, e.g., on p. 377 therein; the surrounding materials, in which he acknowledges a Dollond magnification of 500 as opposed to 300 for his telescope, make one wonder about the meaning of that statement.

It is, incidentally, exceedingly curious that this original success had no follow-up. Why the artisan Ferret (identified as Fenet in Bigourdan's “Un Institut …”, 51), who was responsible for making the flint-glass under Rochon's direction, did not compete for the 12,000 livres prize offered by the Academy in 1786 for the manufacture of that material might be a most interesting study.

On specula composition from Newton to Herschel—including the Copley Medal-winning (1777) efforts of Mudge and the rather more unconventional approach of Edwards—see Moss , “The telescopes of … Herschel”, 7–15, passim; King , The history of the telescope, ch. 5; and David Brewster's chapter on optics appended to his second edition of Ferguson's lectures on selected subjects (2 vols, Edinburgh, 1806), ii, esp. p. 457. The small amount of arsenic served only the refining process and evaporated at the fusion of the copper and tin. See Danjon André and Couder André , Lunettes et télescopes (Paris, 1935), n. 40 on p. 678.

I have also, of course, ignored the ever-present problem of brittleness. It was primarily to attempt to overcome this that Herschel augmented the percentage of copper. On that increase and its outcome, see, inter alia, the already-cited passages in Moss, King, and Dreyer, as well as Lubbock Constance A. , The Herschel chronicle: The life story of William Herschel and his sister Caroline Herschel (Cambridge, 1933), 163, 167.

A summary of work done in England and Sweden during the first decade after its “rediscovery” was published anonymously in Paris in 1758: [Morin], La platine, l'or blanc, ou le huitieme métal. The likelihood of knowledge about it at the beginning of the seventeenth century was made known in an article basic to this study: “Mémoire qui traite du Platine, de son utilité dans les arts, du perfectionnement du Flintglass, & des avantages des Télescopes sur les lunettes achromatiques”, Journal de physique, 1798, 3–15.

Specifically, Bode, who, however, employed the symbol in a hitherto unused position. See Alexander A. F. O'D. , The planet Uranus: A history of observation, theory and discovery (London, 1965), 55; also Lubbock , The Herschel chronicle …, 123.

The final sentence in the incredibly-long full title of the La platine book contains the phrase “Utile dans les Arts, qui peuvent employer cette Substance à fabriquer des Miroirs qui ne se ternissent point à l'Air …”, while the same point is made therein—on the basis of experimentation—generally at p. 24 and specifically with reference to telescopes at p. 29.

Rochon , “Mémoire qui traite du Platine …”, 5, 8–9. The mirror weighed 14 pounds. Carochez and his work have sometimes been unfortunately obscured; see my article “The persistent ghost: The artisan Laroche”, Technology and culture, xii (1971), 69–74. See also below, ref. 91.

As recorded in the manuscript Registre des procès-verbaux des séances housed in the Archives de l'Académie des sciences. In the volume for 1785, see fol. 219 for his reading of the memoir on November 16 and fol. 224 for his presentation of the instrument itself ten days later. Curiously, since both should have known better, the date was reported as later by Cassini, who placed this success in 1786, and by Lalande, who placed it in 1787. Cassini did so in his manuscript Les Fastes de l'Astronomie … T.3: IV^m V^m et VI^m Age. 1600–1800, Archives de l'Observatoire de Paris, D 1, 27, p. 122, while Lalande offered his statement in Bibliographie astronomique; avec l'histoire de l'astronomie depuis 1781 jusqu'à 1802 (Paris, 1803), 672. The latter further stated that the telescope had been taken to Brest. This also seems erroneous; see below, refs 22 and 87.

This paper, read at the Academy's public meeting of 15 November (Registre, 1786, fol. 352), is the one cited in ref. 15 above. The long delay in its publication greatly aided this author by allowing Rochon to add many post-1786 details.

The most important passages ( Rochon , “Mémoire …”, 8) in this connection are the following: “On purifiera à un feu violent le platine en grains par le moyen du nitre & du sel de verre. On joindra au platine qui aura été purifié, le huitième du métal qui sert à la composition des miroirs ordinaires, car l'étain sans cuivre rouge ne produiroit pas un bon effet. On soumettra ce mélange au feu le plus violent, que l'on excitera encore par l'air déphlogistiqué qui se dégage du nitre lorsqu'on le jette dans le feu. Une seule fonte seroit insuffisante; il en faut cinq ou six pour que le mélange soit à sa perfection. Il est nécessaire que le mélange soit dans l'ètat de parfaite fluidité au moment où on le verse dans le moule”. Although Lalande characterized the mirror as being “inattaquable, même par l'eau forte”, he inexplicably had it made “Avec d'alliage …” ( Montucla , Histoire des mathématiques, iii, 502, where he also repeats the 1787 date).

Rochon did not even report a comparison with other instruments. Lalande, on the other hand, stated (Bibliographie astronomique, 672) that it “se trouve meilleur que celui de Dollond qui est à l'Observatoire”. Assuming he meant the Dollond gregorian of 6½ ft length that the Observatory had acquired for its reorganized regime at a cost of 6000 livres, the comparison is not very helpful since the Dollond aperture was only 7 in. See the “Inventaire des instruments de l'Observatoire national de Paris en 1793”, printed as n° X of the “Pièces Justifificatives” of Cassini's Mémoires pour servir …, 208–17. The brief description therein (p. 211) of Dollond's telescope is immediately followed by one of Carochez's (p. 212), which, therefore, was in Paris and not in Brest in 1793. See also below, refs 33 and 87. Cassini's description, incidentally, gave Carochez's telescope an aperture of only 7½ ins.

Smith Robert , A compleat system of opticks in four books (2 vols, London, 1738), i, 142, for a particularly-explicit statement of a frequently-made point.

These studies were, of course, to culminate in the famous paper he read to the Royal Society in November 1799: “On the power of penetrating into space by telescopes …”, Philosophical transactions, xc (1800), 49–85. Herschel showed that the eye received only 43% of the original light with a newtonian telescope but 63% with his front-view type, although “penetrating power” depended on more than the collection of light. The front-view approach had been first attempted in 1728 by Jacques Lemaire in France, where, indeed, it is still designated by his name. Lemaire's not-very-good instrument was “discovered” in the “cabinet du Collège de Navarre” in 1787, whence it was carried to an obviously gleeful presentation to the Academy. See Registre, 1787, fols. 267, 281.

This letter, of 7 January 1787, is quoted in Bigourdan , “Un Institut …”, 51.

The authorization came from le baron de Breteuil, who, as Minister of the King's Household with responsibility for all academic affairs, had been instrumental in carrying out the reorganization of the Observatory. See Cassini, Mémoires …, esp. pp. 21–2.

Ibid., 29.

The Academy had created, in August 1787, a Comité de brevets of seven academicians to examine the works of various artisans in order to judge their merits. The first presentation of candidates was made on 9 January 1788. Of the nine artisans named, six—including Carochez—were elected on 16 January (Registre, 1788, fols. 2, 10).

Bigourdan , “Un Institut …”, 52.

Thus, when the Danish Astronomer Royal, Thomas Bugge, visited Carochez's atelier (although wrongly identifying it as belonging to Laroche; see above, ref. 18) in 1798–9, he reported looking through a platinum-mirrored telescope of 2 ft length which could conceivably have issued from an earlier experimental program. See Science in France in the Revolutionary era described by Thomas Bugge ( Crosland Maurice P. , ed., Cambridge, Mass., 1969), 170. There are problems with such an interpretation, however, beyond the fact that there is nothing in Bugge's account actively to support it. See below, ref. 33.

The use of both names is intended to indicate the difficulty of separating the contributions of Rochon and Carochez. Each, in his own writings, refers to the developments as due to himself, although Rochon supported that claim of Carochez when it was to the letter's advantage. See below, refs 49 and 60. This provision from Trudaine seems to have been in response to a request made of him by Rochon. The Trudaine in question was one of the sons of Trudaine de Montigny, who, as an honorary member of the Academy, had suggested and financed its first flint-glass prize offered in 1767 but awarded only in 1774, and who, as a father, endowed his sons with similar interests. See Maindron Ernest , Les fondations de prix à l'Académie des sciences. Les lauréats de l'Académie, 1714–1880 (Paris, 1881), 26–7; “Eloge de M. Trudaine”, Oeuvres de Condorcet (publiées par O'Connor Condorcet A. et Arago M. F. , 10 vols, Paris, 1847–9), ii, 206–38. Curiously, though Rochon had dealings with such English instrument-makers as Ramsden during a trip to London in May 1790, he does not appear to have visited Herschel. Or, at least, he is not mentioned in the list of visitors provided in King's History of the telescope, 134. On Rochon's offer to undertake commissions for his colleagues in England, see Registre, 1790, 99 (meeting of 1 May). On his request to Trudaine, see his “Mémoire …”, 12. See also ref. 32 below.

Rochon had requested Cassini's participation in such a comparison in a letter of 25 January 1791, in which, after informing Cassini of the status of the instrument ordered for the Observatory from Ramsden, he related information on Trudaine's purchase of the Herschel telescope for 100 English pounds. See Wolf , Histoire de l'Observatoire …, 296–7. (Cf. the more accurate figure of £107 2s. in Dreyer's “Introduction”, p. li.) He was even then confident that the Carochez device would be superior. Though his letter stated that Carochez would have it completed in two weeks, his report on it to the Academy occurred only on 4 May 1791 (Registre, 1791, 333). Unfortunately, as was almost always the case, this comparison—which seems to have been extended to include the Dollond telescope of the same size—placed too much emphasis upon magnification and too little upon light-gathering; see, however, below, ref. 51.

This is a subject which needs much fuller study, Bigourdan, who mentions no developments after the 1788 provision of platinum, contenting himself with the following statement: “les meubles furent dispersés en 1791 et un instant il fut question d'installer les instruments au Louvre; mais finalement ils furent transportés à l'Observatoire de l'Académie” (“Un Institut …”, 52). The statement in his Histoire de l'astronomie d'observation …, 154, is very much the same. According to Rochon (“Mémoire …”, 13), the instrument in question here was transferred in September 1792. The later “Inventaire” (see above, ref. 22) reveals that both platinum efforts, another 7 ft newtonian with, apparently, ordinary mirrors, and the earlier dom Noël device were brought to the Observatory from La Muette—possibly by way of the Louvre ( Cassini , Mémoires pour servir…, 212). The fact that there is no mention of any smaller platinum-mirrored telescopes is the principal problem in the hypothecation of experimental efforts between 1788 and 1791. See above, p. 89 and ref. 30.

Registre, 1791, 45–6, meeting of 21 December 1791.

Lalande , Bibliographic astronomique…, 714. It was Lalande, Herschel's most important and frequent correspondent in France, who read the communication to the Academy. The letter was undoubtedly a summary of the paper that Herschel read to the Royal Society on 15 December 1791: “On the ring of Saturn, and the rotation of the fifth satellite upon its axis”, Philosophical transactions , 1792, 1–22. We are afforded a striking indication of the high esteem in which French astronomers held Herschel's new instrument by Méchain's appreciation of his discovery of Saturn's sixth satellite “avec votre fameux télescope de 40-pieds qui sera toujours l'étonnement et le désespoir des opticiens …” ( Lubbock , The Herschel chronicle, 219).

On this prize, see Maindron , Les fondations de prix…, 50–1.

Registre, 1792, 65 (meeting of 1 February), 94 (meeting of 10 March).

Ibid., 97–8 (meeting of 14 March), 100 (meeting of 17 March).

The proposals were made at the meeting of 24 March (ibid., 110–11).

Lalande , Bibliographie astronomique…, 625, 721.

Registre, 1792, 114.

Ibid., 115. Although the unverified but incontestable discoveries may be such items as the Saturn ring separation, it seems likely that this phrase may also refer to the extraordinary magnification powers that Herschel claimed for his eyepieces. Rochon had earlier declared such “astonishing” but believable. See, e.g., p. v in the Préface to his Recueil de mémoires….

Curiously, since he deals with contemporaneous awards of the Royal Society's Copley Medal to non-Englishmen, Sir Gavin de Beer makes no mention of this development in his The sciences were never at war (New York, 1960). Given Herschel's Hanoverian birth, this award becomes even more international.

Registre, 1792, 116–17.

The class of astronomy then consisted of Lemonnier, Lalande, Messier, Cassini, and, though he had vanished with the Lapérouse expedition, d'Agelet. The Academy's President for 1792 was the duc d'Ayen, who had then taken the safer name of Noailles-Ayen. The acting Secretary, in Cordorcet's Revolutionary necessitated absence, was the cristallographer René Haüy.

On this establishment, from intention through operation, see Ballot Charles , ed., “Procès-verbaux de consultation des arts et métiers”, Bulletin d'histoire économique de la Révolution, Année 1913, 15–160.

In actual amounts, the minimum of the first class was to be 4000 livres, the medium 5000, and the maximum 6000, while in the second class the equivalent amounts were to be 2000, 2500, and 3000 respectively.

Ironically, although the corps had been formed, in part, to circumvent the existing guild system in France—one factor in that nation's instrumental lag—it fell with that system when the Assembly, in March 1791, passed the LeChapelier law suppressing all organizations of workers.

Though ostensibly the work of Borda, Laplace, and Rochon, the report—which dealt mainly with his general platinum mirror success and his recent specific 7 ft example thereof—was undoubtedly written by the latter; indeed, except for its attribution of key developments to Carochez alone (see above, ref. 31), some of its language is identical to that in Rochon's later “Mémoire …”. For the full text of the report see the Mémoires du Bureau de Consultation des Arts, ou Journal des inventions, découvertes et perfectionnemens dans les sciences, arts, et métiers , i (Huitième Cahier, I^er Trim. 1793), 30–1. For the Bureau's summary and action on it, see Ballot , “Procès-verbaux …”, 43. Since the report related the comparisons made by Méchain and Cassini, those two individuals were invited to concur in its statements; they did so with alacrity.

The comparison itself seems to have been made by Méchain and Lalande in 1788. See Lalande , Bibliographie astronomique …, 836.

Interestingly, Méchain complained of the loss of distinctness at the edges of objects in Herschel's telescope by virtue of “la grande lumière qu'il répandait sur le champ de l'observation” (Registre, 1792, 166). He attributed the large amount of light to the suppression of the small mirror and could not resist pointing to Lemaire's original execution of that approach.

Ibid., 167.

Ibid., 166–7, where the Polish general's name is given as Komarowski.

I am omitting the question of the proposed telescope's mounting since that is irrelevant to the purpose of this paper and, in any event, no final decision was arrived at in regard to the artisan most appropriate for that work, although Delambre did suggest that it could be “dirigée et éclairée” by a mechanician such as Perrier, by whom he undoubtedly meant to indicate his colleague in the Academy, J. C. Périer. Cf. the brief indication in one of the two paragraphs devoted to this entire episode—and containing several erroneous statements—in Daumas, Les instruments …, 228. See also below, refs. 78 and 94.

Registre, 1792, 144. The Academy commission's meeting with the Committee took place on 7 May and is duly recorded in Guillaume James , ed., Procès-verbaux du Comité d'instruction publique de l'Assemblée Nationale (Paris, 1889), 271.

Registre, 1792, 116.

Ibid., 144. The precise amount was 32,300 livres 8 sols 4 deniers. See Maindron , Les fondations de prix …, 6, and Oeuvres de Lavoisier publiés par les soins de son Excellence le Ministre de l'Instruction Publique et des Cultes ( Dumas J. B. et Grimaux E. , eds., 6 vols, Paris, 1862–93), vi, 39.

Registre, 1792, 144–5.

Fortunately, the discussion, from which the following account—including the quotation—has been taken, was fully reported in the minutes (ibid., 146–7).

See the “Note manuscrite sur Carochez écrite par lui-même” under the designation of P. 87 in the Archives du Conservatoire national des Arts et Métiers, which Parisian depository I should like to thank for providing me with microfilms of this document and the Rochon report (see above, ref. 49).

Procès-verbaux du Comité…, 312.

A résumé of this joint discussion, which took place in the Academy's meeting room in the Louvre on 31 May, was read at the Academy's meeting of 6 June and recorded in full in Registre, 1792, 163–7.

Une ligne.

Pierre-Bernard Mégnié had been hired, at the recommendation of Lalande, for the Observatory's instrument program in 1785, but had disappeared therefrom in 1786. See Wolf , Histoire de l'Observatoire …, 278–9, 282–3, and Daumas , Les instruments …, 360–2. Mégnié subsequently turned up in Spain and resumed a relationship with Lalande, who, however, appears to have here credited him with something that he had not achieved. Certainly, at least, it was not related in a letter to Lalande, who read it to the Academy in February 1790, in which Mégnié discussed the mirrors he had made by that time for the Royal Observatory at Madrid. See Registre, 1790, 62.

Based, apparently, upon offers made by one Mendoza, who, according to Lalande, was an “habile officier de la marine d'Espagne” (Bibliographie astronomique …, 761). For the same individual's later negotiations with Herschel, see below, ref. 90.

Procès-verbaux du Comité …, 331.

This is implied in a “Mémoire” on this subject entered into (pp. 368–9) the Registre for 1793, which, however, does not really contain minutes, but consists of reports, letters, etc., entered rather haphazardly. It is stated in this memoir that “Les travaux importants dont l'assemblée Législative a été occupée dans les derniers momens de son existence, lui ont fait perdre en vue cet objet particulier …”. For the dating of this document, see ref. 69.

The source of this item of information is a 1799 report to the First Class of the National Institute, the purpose of which will become clear below ( Procès-verbaux des séances de l'Académie tenues depuis la fondation de l'Institut, jusqu'au mois d'août 1835 (10 vols, Hendaye, 1910–22), i, 611). Although the report contains several errors (see, e.g., below, ref. 91), this particular fact is mentioned twice with such specificity (see ref. 70 below) that it compels acceptance despite the facts that I have not been able to find any contemporary evidence of this delivery and that France's relations with Spain were very poor after 10 August 1792. There is absolutely no mention of Spanish platinum, for example, in the relevant volumes (somewhat over the first 1½ vols) of both Guillaume , ed., Procès-verbaux du Comité d'instruction publique de la Convention nationale (6 vols, Paris, 1891–1907) and Aulard F. V. A. , ed., Recueil des actes du Comité de salut public avec la correspondance officielle des représentants en mission et le registre du Conseil exécutif provisoire (28 vols, Paris, 1889–1951). Similarly, Carnot's long report on Spain and the impending war with that nation is silent on this bit of Spanish collaboration: Correspondance générate de Carnot avec notes historiques et biographiques par Etienne Charavay (4 vols, Paris, 1892–1907), i, 323 ff.; see also Reinhard Marcel , Le grand Carnot, l'organisateur de la victoire, 1792–1823 (Paris, 1952), esp. chs 1–2. See also below, ref. 70.

This abandonment and the offer to be dealt with shortly were the purposes of the “Mémoire” of ref. 67, which is undated and located in the midst of materials of May 1793. It has been printed by Maindron (Les fondations de prix …, 6–7) and correctly assigned by him to March. That assignation is borne out by the fact that the Academy's proposal was read to the Convention on March 18. If further confirmation were needed, it would be provided by the total absence of any mention of the telescope project in Lavoisier's summaries of the Academy's post-March activities. See his “Notice sur les travaux des Sociétés savantes de Paris pendant le mois d'Avril 1793, et une partie du mois de Mai dernier”, in Scheler Lucien , Lavoisier et la Révolution française. I: Le Lycée des arts (nouvelle édition, Paris, 1957), 28–41 and the continuation “Extrait des travaux de l'Académie des sciences pendant les mois de mai et de juin”, Oeuvres de Lavoisier ( Dumas J. B. and Grimaux E. , eds., 6 vols, Paris, 1862–93), vi, 61–3. On the other hand, Maindron's statement that the “Mémoire” was addressed to the Committee of Public Instruction seems incorrect, for it does not say this nor was it presented to that committee, whose Procès-verbaux are totally silent on the subject except for Guillaume's inclusion (ii, 442–3) of the minutes of the Convention's meeting of 18 March.

The use of 490 hectograms to this end is one of the specific points made in the 1799 report (ref. 68). Although the various works dealing with the metric system discuss the use of platinum in the étalons and the dilation experiments which preceded that employment (as well as such other applications of the metal as in the platinum wire pendulum observations of Borda), they do not indicate the source of the material. See, e.g., Delambre J. B. J. and Méchain P. F. A. , Base du système métrique décimal, ou mesure de l'arc du méridien compris entre les parallèles de Dunkerque et Barcelone, exécutée en 1792 et années suivantes, par M M Méchain et Delambre (3 vols, Paris, 1806–10); Bigourdan G. , Le système métrique des poids et mesures, son établissement et sa propagation graduelle avec l'histoire des operations qui ont servi à déterminer le mètre et le kilogramme (Paris, 1901); Favre A. , Les origines du système métrique (Paris, 1931). The Lavoisier notices of the previous are also devoted to the metric “standards” works then in progress; they are equally silent on the subject of Spanish platinum.

For a brief analysis of the interpretive problems surrounding the suppression of the Academy in August 1793 and the literature dealing with them, see my “The Academy of Sciences during the eighteenth century; an astronomical appraisal”, French historical studies, v (1968), 371–404. The most recent treatment of the subject, and one which clearly will become the new standard, is that by Hahn Roger : The anatomy of a scientific institution: The Paris Academy of Sciences, 1666–1803 (Berkeley, 1971).

That the Committee of Public Safety did this is another unverified statement of the 1799 memoir. Aulard's Actes are again mute on this matter. But see ref. 73.

Though not mentioned in the procès-verbal of the meeting of 2 Fructidor IV, this resolve (incorrectly dated 2 Frimaire in the 1799 memoir) was found among certain minutes of that day in “les dossiers correspondants” and printed in the notes following the meeting in Debidour A. , ed., Recueil des Actes du Directoire Exécutif (4 vols, Paris, 1910–17), iii, 399. Since this seems to be the first mention of platinum by the Directory, it remains unclear whether this governing body or its predecessor was responsible for this acquisition.

Procès-verbaux des séances de l'Avadémie …, i, 87.

Ibid., 92–3. The Debidour source of ref. 73 reveals the Directory's receipt of a letter, dated 18 Fructidor, from the Secretary of the Institute.

Procès-verbaux des séances de l'Académie …, i, 317–18.

Ibid., 411. Here also the date of the Directory resolve was reported as 2 Frimaire. It seems likely that these slips stemmed from misinterpretations of the abbreviation Fr.

Interestingly, the latter was the same Périer J. C. who had been suggested as the mounting “overseer” for the original telescope project. See above, ref. 54.

The 1799 report reveals that these experiments were made with a part of the “weights and measures” platinum, the three boxes of the new shipment having been “déposées dans une armoire, où elles existent dans leur intégrité” (ibid., 611). As will be seen shortly, the condition of the “Rochon” telescope demonstrated a need for such experimentation. See below, ref. 87.

Ibid. , 607. On Guyton's experiments, see Bouchard Georges , Guyton-Morveau, chimiste et Conventionel (1737–1816) (Paris, 1938), 353. For the fate of Guyton's request, see below, ref. 91.

Ibid., 610–13. This is the frequently-cited 1799 report.

This is not meant to imply that the First Class was simply a recreated Academy. On this important question, compare the early and late treatments of Roger Hahn: “The National Institute of France, First Class (1795–1803): A study in change and continuity” (A.B. thesis, Harvard University, 1953) and The anatomy of a scientific institution, ch. 10.

My italics—to draw attention to the magnification involved in the rumours.

Science in France …, 110.

Bugge's reaction was as follows: “I must here observe, that the optical and astronomical rhodomontade of a gigantic reflecting telescope of sixty feet, with a platinum speculum, said to have been made here, has no foundation, and has not been heard of …” (ibid.). The remainder of Rochon's statement went even further in alleging “que l'on ne songe même pas à le réaliser” (“Mémoire qui traite …”, 13).

Lalande , Bibliographie astronomique …, 798–9. For a suggestion as to what he might have been talking about, see below, ref. 94.

It is not at all clear from Bugge's account whether he examined one or both of the two earlier telescopes, or, if the former, which one was involved. He deals with this subject twice, remarking on the first occasion that Bouvard showed him “the platinum specula of Rochon's telescope”. This examination provided the quotations in the text, to which one might add that he thought the dark speckles “were undoubtedly owing to the platinum not being perfectly purified before the speculum was cast; and it still contained some small quantity of iron” (Science in France …, 109). On the second occasion, he went to the Observatory with Carochez and compared the latter's newly-ground 6 ft “achromatics” with the “Rochon” telescope. He then found that “the reflector not only magnified much less, but gave a remarkably brown reflection, and an obscure and confused image …” (ibid., 119). Incidentally, Rochon's 1798 hopes for the 1791 telescope would seem to conflict with these characterizations, or, at least, the latter one: “J'ai lieu d'espérer que le ministre de l'intérieur aura égard à ma demande, et qu'il ne tardera pas à faire jouir l'observatoire de la marine au port de Brest, d'un instrument qui peut lui être très-utile” (“Mémoire qui traite …”, 13).

He was here examining the 2 ft mentioned in ref. 30 (Science in France …, 170).

For the names of the participants and a brief analysis of all of their efforts, see Maurice Crosland, “The congress on definitive metric standards, 1798–1799: The first international scientific conference?”, Isis, lx (1969), 226–31. The public ceremonies on 22 June 1799 surrounding the presentation of the prototype standards of the metre and the kilogram may also have had some beneficial effect.

This order was placed in 1796, and Mendoza, who was then in London, was charged with pressing its execution ( Lalande , Bibliographie astronomique …, 771). On this 25 ft instrument, which probably never reached its destination, see also in ibid., 814 and in Lubbock , The Herschel chronicle, 177, 261, 319. Most interestingly, the list of Herschel's telescopes provided by Dreyer (“Introduction”, l-li) includes a 7 ft ordered by Mendoza with the indication “Platina Spec”. Although undated, this indication suggests, of course, that the Spanish may have turned to Herschel for a platinum-mirrored telescope when the French project collapsed. Inasmuch as the list shows no payment to Herschel for this device, it must be presumed that he did not succeed in this venture, a not-surprising result in view of the fact that Carochez's request for a national recompense (see ref. 60 above) tells us that “Le célcbre Monsieur Herschel ne pouvait croire qu'on fut parvenu en France, à … des Miroirs de platine…. Lui a paru sinon une chose impossible du moins une invention dont il desire fortement verrifier l'existance …”.

Procès-verbaux des séances de l'Académie …, i, 612. Among the related expenses foreseen were the costs of construction “des ateliers, des fourneaux, des forges, soit pour mouler un disque de pareil volume, soit pour le souder par la malléation, et de nouvelles machines pour en travailler régulièrement la courbe et lui donner le fini”. The report did not state that these latter items would be done by the experienced Carochez, who, in fact, was misidentified in reference to the earlier project, as Lerochez. Finally, although the instruments desired by Guyton were estimated to need only about 15 hectograms of platinum, the report felt it was important to “ne pas morceler l'approvisionnement destiné à un plus grand projet” and so called for an additional purchase of the metal to that end.

This is Lalande's characterization of the existing situation (Bibliographie astronomique …, 809).

On this point, and the related one of the following paragraph, see, e.g., the articles by Charles Webster K. Sir and Humphreys R. A. reprinted, respectively, as “British, French, and American influences” and “Isolation from Spain”, in The origins of the Latin American revolutions, 1808–1826 (ed. with an Introduction by Humphreys R. A. and Lynch John , New York, 1965), 75–83, 138–47.

Although with an unaccounted-for change in length, since Lalande credits Bonaparte with raising hopes for “deux milliers de platine pour faire un télescope de 36 pieds, qui surpassers probablement tout ce qu'on a fait jusqu'ici …” ( Montucla , Histoire des mathématiques, iii, 502). At about the same time, but in another place, Lalande stated that Carochez was currentlyoccupied with making a “front-view” platinum-mirrored telescope of 7½ in. aperture (Bibliographie astronomique …, 835). His immediately-prior mention of Carochez's new reworking of the dom Noel 22 ft and subsequent reference to the fact that the Bureau des longitudes, to which Carochez was attached as instrument-maker, wanted this done in platinum (ibid., 855) appears to have caused some of Daumas's confusion (see above, ref. 54) (Les instruments …, 228, 373). Might this also have been the source of the rumours of 1798? Although one problem with this interpretation would be the fact that the Bureau did not decide upon the reworking until February 1799, it seems logical to suppose that the idea was being discussed considerably before that time (G. Bigourdan, “Le bureau des longitudes. Son histoire et ses travaux de l'origine (1795) à ce jour”, Annuaire (publié par le Bureau des longitudes), 1931, A 2–3).

For some details on this work and the problems he encountered, see Williams Pearce L. , Michael Faraday, a biography (New York, 1965), 116–20.

King , The history of the telescope, esp. p. 178.

The scientific papers of William Parsons, Third Earl of Rosse, 1800–1867 (collected and republished by the Hon. Sir Charles Parsons, London, 1926), 53–5, 68, 109, 145. Rosse was led to this experimentation by a reading of an article by Jamin J. : “Mémoire sur la couleur des métaux”, Annates de chimie et de physique, Troisième Série, xxii (1848), 311–27; see esp. p. 321. Unfortunately, Jamin did not include platinum in his investigations.

On that development, see King , The history of the telescope, esp. ch. 13. It is not clear to me whether Liebig's silvering process could have employed platinum, but certainly this could have been achieved by more recent electrolytic techniques. That this has not, to my knowledge, been attempted is probably the result not so much of expense but of the emergence of aluminum coats, which combine the non-tarnishing characteristic with excellent reflectivity, not only with visible light but with ultraviolet as well. See in ibid., 382, and in Danjon and Couder , Lunettes et télescopes, 562–7.