376 



NATURE 



[August 20, 1903 



falling in front of a vibrating tuning fork to which a 

 suitable style is attached. It may interest Mr. Millikau 

 to know that this device has been used by students at 

 the London Royal College of Science for the last twenty 

 years. Similarly the vapour-tension device is an improved 

 form of the bent tube with the shorter limb closed and 

 with mercury in the bend which has long been used in 

 laboratories in this country for the determination of boil- 

 ing points. 



The additions to the Zoological Society's Gardens during 

 the past week include an Anubis Baboon {Papio anubis) 

 from West Africa, presented by Mrs. J. B. Ward ; a White- 

 crowned Mangabey (Cercocebus oethiops) from West 

 Africa, presented by Mrs. Stevenson ; a Green Monkey 

 (Cercopithecus callitrichus) from W'est Africa, presented by 

 Mr. F. W^ A. Jackson, R.A. ; a Black Rat {Mus rattus), 

 British, presented by Mr. Oswald M. Courage ; six English 

 Vipers {Vipera berus) from Dorset, presented by Mr. A. 

 Old ; two Slender Loris (Loris gracilis) from Ceylon, a 

 Black Hornbill {Sphagolobus atratus) from West Africa, 

 three Westerman's Eclectus (Eclectus westermani) from 

 Moluccas, ten Common Skinks (Scincus officinalis) from j 

 North Africa, deposited ; a New Zealand Parrakeet j 

 (Cyanorhamphns novae-zealandiae), a Golden-headed Parra- ', 

 keet (Cyanorhamphus auriceps) from New Zealand, pur- j 

 chased; a Garnett's Galago {Galago garnetti) from East 1 

 Africa, a Stanley Crane {Anthropoides paradisea) from ' 

 South Africa, received in exchange. 1 



OVR ASTRONOMICAL COLUMN. 



The Spectrum of Comet 1903 c. — On July 14 and 15 

 Dr. Curtis, of the Lick Observatory, found that the visual 

 spectrum of this comet consisted of a strong continuous 

 spectrum, and the three characteristic cometary bands, that 

 at A. 4770 being by far the brightest. He tried to photo- 

 g-raph the spectrum by giving a six hours' exposure with 

 the 36-inch telescope, but obtained no result, the intrinsic 

 brightness of the comet being too small. 



Prof. Perrine, using a small slit spectroscope with the 

 Crossley reflector, obtained a spectrum with four hours' 

 exposure, and found that it contained the five bands 

 obtained by Campbell in Comet b 1893 (Rordame) and in 

 Comet h 1894 (Gale), viz. 388, 409, 421, 436 and 473. The 

 bands obtained by Perrine also agree in brightness with 

 those previously photographed, with the exception of that 

 at \ 420, which was one of the brightest bands in the 

 former comets, but is very weak in this one (Lick Observ- 

 atory Bulletin, No. 47). ' 



The Spectroscopic Binary ;8 Scorpii. — Working with 

 the new spectrograph of the Lowell Observatory, Mr. 

 \. M. Slipher has determined that the spectroscopic binary 

 J8 Scorpii has a very wide range of velocity, extending over 

 250km. from —109km. to -f-146; these variations are 

 satisfied by a period of 6d. 2ih. 



The spectrum of each of the components is of the Orion 

 type, and the velocity determinations were made from 

 measurements of the lines H^, A 4388, and A. 4472 (Lowell 

 Observatory Bulletin, No. i). 



Effects of Absorption on the Resolving Power of 

 Spectroscopes. — In a mathematical discussion of the 

 manner in which the absorption of a train of prisms affects 

 the resolving power of a spectroscope. Prof. Wadsworth, 

 of the Allegheny Observatory, has found that for small 

 absorption values the actual resolving power is practically 

 identical with its theoretical value, but as the absorption 

 increases a most important diminution of the resolving 

 power takes place. So rapid is this diminution that in 

 several actual instruments now in use, which were designed 

 to give great resolution, this end has been defeated bv the 

 high absorptive power of the dense flint prisms used in 

 their prism-trains. Thus in the Young spectroscope, the 

 theoretical resolving power in the neighbourhood of the 



NO. 1764. VOL. 6^'] 



H and K lines is 300,000, whilst the practical power is 

 only about 57,000, actually less than that which an instru- 

 ment one-fourth the size would possess. 



Prof. Wadsworth summarises the results of his discussion 

 in the following statements. "It is at once evident from 

 these results that if high-power prism spectroscopes are to 

 be used in the investigation of the photographic region of 

 th.» spectrum, the use of extra dense flint glass, so 

 commonly employed in the past, must be avoided, not only 

 on the score of light-efliciency, but, as now appears, on the 

 score of photographic resolving power and purity as well. 

 The use of lighter flint reduces the theoretical resolving 

 power of any given prism train by decreasing the value 

 of the dispersion coefficient, but this may be easily, and 

 even advantageously, compensated by increasing the re- 

 fracting angle of the prisms." 



Many new spectroscopes have been designed on the 

 principle enunciated above, amongst others those of the 

 Allegheny, Lowell, and Philadelphia Observatories may be 

 mentioned (Miscellaneous Scientific Papers of the Allegheny 

 Observatory, No. 11). 



A New Circumzenithai. Apparatus. — A novel apparatus 

 for determining zenith distances has been devised by 

 Fr. Nusl and M. J. J. Fric, of Prague, and is described 

 and illustrated in a Bulletin International de I'Academie des 

 Sciences de Boheme. 



The accompanying diagram shows the essential features 

 of the apparatus. When the star E approaches the altitude 

 i8o-a it forrtis, at 

 the focus of the 

 telescope O, two 

 images, one of 

 which has been re- 

 flected directly from 

 the face AC of the 

 prism ACB, the 

 other from the face 

 CB after reflection 

 from the surface of 

 a bath of mercury 

 HH ; these two 

 images coalesce at 

 the moment that 

 the star crosses the 

 zenith circle at alti- 

 tude i8o-a, and tha c 

 moment is chrono- 

 graph i c a 1 1 y re- 

 corded. Numerous improvements have been made on the 

 original design, the chief of which consists in sub- 

 stituting two mirrors inclined to each other at the angle a 

 in place of the prism shown here, and, by inserting small 

 prisms, the star images are observed as sharply defined 

 horizontal lines. Using a telescope of 350mm. focal length 

 and 40mm. aperture, with a 50 eye-piece, a determination 

 of time correct to +005S. — oo6s. may be made, and by 

 observations of three stars a determination of latitude 

 correct to ±o"-22 is easily performed. 



The Secchi Commemoration. — The twenty-fifth anni- 

 versary of the death of Padre Angelo Secchi was com- 

 memorated at the Collegio Romano last spring, when an 

 address was read by Prof. Elia Millosevich. This has since 

 been published, with a portrait of Secchi, by the Press of 

 the Lincei Academv. 



THE NEW YORK ZOOLOGICAL SOCIETY.* 

 A LTHOUGH the preservation of the native animals of the 

 -^ United States is one of the avowed objects of the New 

 York Zoological Society, the establishment of small parks, 

 where the larger species can live and multiply under con- 

 ditions approximating as nearly as may be to their natural 

 surroundings, has been specially undertaken by the sister 

 society at Washington. And, so far as we gather from the 

 report before us, the authorities at New York are direct- 

 ing their attention to the exhibition of animals from all 

 parts of the world on an equal footing. Considering that 

 the year (1902) to which the report relates is only the fourth 

 Seventh Annual Report of the New York Zoological Socleiy." Pp. 



205 ; illustrated. (Nev 



.eport I 

 York, 



1903-) 



