For the curious reader, these measurements were made by the physicist J. Violle (1841–1923) who, observing from Mont Blanc, found in 1875 a value of 2.54 cal cm2min−1 for the solar constant. See my Discovery of the universe (London, 1957), 157.
2.
These developments are covered in my booklet Astronomical photography (London, 1961).
3.
The conversion of hydrogen into helium was explicitly suggested as the source of stellar energy by Perrin in 1919 (see CoudercP., L'Astronomie, lxi (1947), 1–10).
4.
I would view more favourably the ultimate value of the “Astrographic Catalogue” work which will steadily increase with time because it provides the earliest ‘first epoch’, hence the longest time base for the determination of proper motions of millions of faint stars.
5.
Surprisingly, the latter fails to mention the two most widely used microphotometers in French laboratories and observatories — including Haute-Provence — during the period: First the visual instrument of Fabry and Buisson, and later the photoelectric microphotometer built by D. Chalonge in 1926, a great advance on the clumsy electrometer device of Koch, and on the unstable thermocouple instrument of Moll (this reviewer has used all of them at one time or another during the past 50 years).
6.
For example, a 73-cm refractor listed as built for Paris Observatory in 1885 never existed; originally ordered by LeVerrier, but built only after his death (1877), it eventually became the Meudon Observatory double refractor (installed 1889–91). Then, the objectives of this instrument are incorrectly identified (p. 53): It is the visual refractor that has an 83-cm objective, and the photographic has the 62-cm objective, not the reverse. The source of this mix-up appears to be Table V in Agnes Clerke's famous A history of astronomy in the nineteenth century (3rd edn (London, 1893), 553).
