282 



NA TURE 



[January 23, 1902 



This is the number given on the tables of atomic weight 

 issued by the German Chemical Society. Hinrichsen's method 

 consists in the conversion of extremely pure Iceland spar into 

 oxide of calcium. The only measurable impurity present in 

 the spar was iron, the amount of which expressed as ferric oxide 

 was "032 per cent. The conversion into oxide was effected in 

 specially constructed platinum crucibles, the latter being heated 

 in an electric oven at a temperature of 1200-1400° C. Four 

 determinations of the atomic weight gave respectively 40' 144, 

 40'I4I, 40'I42 and 40"I4J — mean =40'I42. This number 

 deviates considerably from that which up to the present time 

 has been generally accepted. 



In a paper on the fossil shells of the Colorado desert, pub- 

 lished in a recent issue (No. 1256) of the Proceedings of the 

 U.S. Museum, Dr. R. E. C. Stearns gives an interesting 

 account of the formation of the desert itself. Surrounded by 

 mountains except in the south, where it opens out, the 

 Colorado desert of California was evidently once an extension 

 of the Californian Gulf, which must once have reached inland 

 some two hundred miles further than at present. The separation 

 of the upper end of this old gulf, now forming the desert, has 

 been caused by the sediment brought down on the east side by 

 the Colorado river, which gradually silted up this portion of 

 the gulf till the present desert area was isolated. Throughout 

 the desert are to be found thousands of small fresh-water sub- 

 fossil shells, mostly referable to the genera Paludestrina and 

 Physa, which appear to have been transported partly by whirl- 

 winds, but chiefly by birds. Some of the species of these 

 molluscs are still living in certain localities in the desert. The 

 remarkable variation exhibited by the shells of certain species 

 is described in detail. 



The additions to the Zoological Society's Gardens during the 

 past week include a Green Monkey (Ceiropi/heciis calHlrichus) 

 from West Africa, presented by Mr. F. S. Davidson ; a Ver- 

 reaux's Guinea-fowl (Ciiitera edouardi), a West African Python 

 (Python sebae,\a.x. nalalensis) from Natal, presented by Mr. 

 W. Champion ; a Hudson Bay Squirrel {Sciunis hiidsoniiis) 

 from the Rocky Mountains, presented by Mr. Edward 

 Whymper ; a Lesser Sulphur-crested Cockatoo (Cacatua siil- 

 f/iurea) {torn Moluccas, deposited. 



OUR ASTRONOMICAL COLUMN. 



DlMENSION.S OF THE Pl.ANETS AND SATELLITES. — In the 

 Asironomiscke Nachrichten (Bd. 157, No. 3760), Prof. E. E. 

 Barnard presents a .series of revised reductions of measures 

 made at the Lick Observatory in 1894 and 1S95, together with 

 recent determinations with the 40-inch refractor at the Verkes 

 Observatory. 



Mercury. — The measures of diameter were made in the day- 

 time, when the disc of the planet was little brighter than the 

 sky background. Powers of 230, 460 and 700 diameters were 

 used, and a piece of amber-coloured glass was placed as a screen 

 over the eye-piece. The resulting mean value of the diameter 

 was 2965 miles. During the observations the disc of the 

 planet was carefully examined for the linear canal system de- 

 scribed by other workers, but no such markings were seen. 

 Under excellent conditions (especially on August 31, 1900), 

 however, decided detiiils in the form of three or four large 

 darkish spots were readily distinguished, and were comparable 

 to the markings on the moon as seen with the unaided eye. 



Venus. — Measures were made of this planet specially to de- 

 termine the extent of variation due to irradiation ; night and 

 day measures were both made with the full aperture of 40 inches, 

 but the amber screen was used for the day series. The value 

 obtained for the irradiation was o"'25. The day diameter of 

 tlie planet is given as 7713 miles. A series of dusky mark- 

 ings were the only features observed on the disc, similar to but 

 fainter than those on Mercury. 



Minor /VrtH«/^.— -Measures of the albedos and diameters of 

 NO. 1682, VOL. 65] 



the four chief asteroids were obtained, with the following 



results : — 



.Albedo. 

 Mars = I. Diameter. 



Ceres ... 0'67 ... 477 miles. 



Pallas ... 0-88 ... 304 „ 



Juno ... i'67 ... 120 ,, 



Vesta ... 277 ... 239 „ 



As seen in the 36-inch and 40-inch telescopes the discs of 

 such asteroids as are measurable always appear well defined 

 and round, with no traces of markings on their surfaces. The 

 corrected values for the other planets are as under: — 



No markings were observed on Neptune, and its disc alway- 

 appeared round. 



Harvard College Observatory Rei-ort, 1901. — In his 

 report for the year ending September 30, 1901, Prof. E. C. 

 Pickering first mentions that of the three important astronomical 

 events of the year, the Harvard College (Observatory staff only 

 participated in the determination of the light variation of Eros 

 and the complete investigation of the changes of Nova Persei. 

 The reason why no measures of Eros for parallax were made 

 was that some fifty other institutions were cooperating in the 

 work, rendering ot)servalions at Harvard unnecessary ; in the 

 case of the total eclipse in Sumatra the conditions were not con- 

 sidered sufficiently favourable to justify any large expenditure. 



East Equatorial. — This instrument has been employed, as 

 in former years, for photometric light comparisons with the achro- 

 matic prism polarising photometer ; more than 16,000 settings 

 have been made, including 1224 measures of the magnitude of 

 Nova Persei. For double stars, &c., too close for examination 

 with the above instrument, a second photometer has been 

 adapted, and 2278 settings made with it. Other work with 

 this equatorial has been the photometric measurement of 

 Jupiter's satellites while undergoing eclipse, the light variations 

 of the minor planet Eros and the asteroids Vesta and Terci- 

 dina, comparisons of long-period variables, and the selection 

 and measurement of twelfth-magnitude standards. 



West Equatorial. — This has been employed for similar photo- 

 metric work on variables and comparison stars. 



Meridian Circle. — Work with this instrument has chiefly 

 consisted of zone observations to compare results obtained by 

 use of crossed spider threads or ruled glass plates. The con- 

 clusions have been published in Annals, vol. xli. No. 7. 



\l-inch Meridian Photometer. — With this instrument 54,448 

 settings have been made by the director on 126 nights. .-V 

 catalogue of 9233 Durchmusterung stars has been completed, 

 and the planet Eros observed on 56 nights. 



Meridian Photometer.— 7,^,^16 settings have been made on 

 98 nights, the principal work being the ob.scrvation of a cata- 

 logue of 376 standard stars of the fifth magnitude ; also com- 

 parison stars for Eros and other similar objects. 



Henry Draper Memorial. — With the II -inch Draper tele- 

 scope 673 photographs have been obtained, and with the 8-inch 

 instrument 1766 photographs. The total number of photographs 

 taken during the year was 40S1. Two new variables, three 

 stars with peculiar spectra, and the presence of bright hydrogen 

 lines in the spectrum of U Andromed.x, have been detected. 

 Photographs of the spectrum of lightning were obtained with 

 the Draper telescope with objective piism during the summer. 



Respecting the production of stellar spectra two new devices 

 are announced. For photographing the sjiectra of stars near 

 the horizon, below 10° altitude, the plan has been adopted of 

 turning the objective prism by a computed amount so as to 

 correct for the atmospheric refraction in declination. The stellar 



