MOUNTAIN OBSERVATORIES IN AMERICA AND EUROPE. 57 



Markings on the discs of Jupiter s satellites have been systematically 

 studied.* 



Precise determination of star-places : Mr. Tucker's , observations of 

 star-positions (not yet published) extend over 2^ years, and comprise 

 about 5000 determinations of some 300 stars. The probable error of 

 a single E. A. is 0« .020 ; of a single Decl. 0".25. 



Photography of the Moon^ Milky- Way ^ and Comets: The photography 

 of the Moon.f Milky-Way, X and of Comets, § and photographic-photo- 

 metric I experiments have been very successfully carried on here, under 

 highly favorable conditions. 



Photography of the Sun : More than 1700 negatives of the sun have 

 been made at Mt. Hamilton by Mr. Perrine with the 40-foot photo- 

 heliograph. The best of them are extremely good, showing fine detail 

 in the spots and of the faculse, and permitting a subsequent enlarge- 

 ment of some 6 diameters. The average negative shows considerable 

 detail. There is no doubt, however, that much of the excellence of this 

 long series arises from the care with which the best moments for ob- 

 servation have been chosen, and that the average negative exhibits 

 something better than the average seeing. 



Spectroscopic observations : Good definition of star-images and great 

 transparency of the air are powerful aids to spectroscopic observations, 

 both visual and photographic. 



Professor Campbell's spectroscopic observations have resulted in a 

 catalogue of 37 lines in the spectra of different nebulae. ^ 



Likewise, the Lick Observatory observations of comet-spectra record 

 3:4 bright lines.** 



The new star of 1892 {Nova Aurigce) showed 32 lines in its visual, 

 and about 50 lines in its photographic, spectrum to Professor Camp- 

 bell, against a materially less number elsewhere catalogued, f f 



Nineteen lines were registered in the spectrum of Nova Aurigce in 

 August to November, 1892, after the change in the spectrum. :|:t 



The nebulous character of Nova Normce was determined §§ when its 

 altitude was less than 2^° ; and both bright and dark hydrogen lines 



* Publications of the Astronomical Society of the Pacific, vol. in, p. 359. 

 f Publications of the Lick Observatory, vol. in. 

 :}: Astrophysical Journal, vol. ll, p. 58, and elsewhere. 



§ Knoivledge, 1891, p. 229 ; Astronomy and Astrophysics, 1893, p. 937 ; Publi- 

 cations of the Astronomical Society of the Pacific, vol. vii, p. 161. 

 II Contributions from the Lick Observatory, No. 3. 

 TT Astronomy and Astrophysics for May and Jinie, 1894. 

 ** Publications of tlie Astronomical Society of the Pacific, No. 31. 

 ^ Ibid., No. 26. 

 tt Ibid. 

 g§ Astronomy and Astrophysics for April, 1894. 



