August 29, 1895] 



NATURE 



421 



logical and kindred sciences, and includes the important collec- 

 tion of the late I'rof. II. Dove. It is arranged under subjects, 

 with the titles under each entered according to authors or 

 institutions, while an alphabetical index at the end facilitates 

 the reference to the subject catalogue. Opinions differ as to the 

 best method of publishing such a work, the strictly alphabetical 

 arrangement, such as followed by Prof. G. Mellmann in his 

 excellent Repertorium der Deutsche)! Meteorologie , or the Royal 

 Society's catalogue of scientific papers, possesses great advan- 

 tages, and obviates the necessity of indexing one book under 

 several sections ; but as the Seewarte originally adopted another 

 method, it has perhaps done well to keep to the same plan, and 

 has rendered good service to science by its careful preparation 

 and timely publication of the catalogue. The first part was issued 

 in the year 1890. 



The additions to the Zoological Society's Gardens during 

 the past week include a Rhesus Monkey (Macacus rhesus, i ) 

 from India, presented by Mr. Hugh H. CoUis ; a Macaque 

 Monkey (Mtuacus cynoinolgiis, i ) from India, presented by Mr. 

 E. Laundy ; a Vervet Monkey (Cercopitheciis lalaiidii, 9 ) from 

 South Africa, presented by Mrs. Edward Webb ; two Brown 

 Capuchins [Cebus faliielliis) from Guiana, presented by Major 

 W. S. D. Liardet ; two Black-eared Marmosets (Hapale 

 iienicillala) from South-east Brazil, presented by Mrs. H. V. 

 Friend ; a Suricate (Stiricata tetradactyla) from South Africa, 

 presented by Mr. J. Lewis ; a Purple-capped Lorj' (Loriiis 

 domicella) from Moluccas, presented by Mr. T. Bailey ; two 

 Tarantula Spiders (^la^'^'^'''^' ^P- ™'^-) from Trinidad, presented 

 by Mr. J. Hoadley ; six Grey Parrots (Psillcuus erithacus) from 

 West Africa, deposited ; a Collared Fruit Bat (Cynonycteris 

 (ollaris), a Vpecha Rail (Aramides ypecaha), bred in the 

 Gardens. 



OUR ASTRONOMICAL COLUMN. 



Reappearance of Swift's Comet.— The Edinburgh 



Circular, No. 44, publishes a telegram from Kiel announcing that 



Comet Swift was seen by Mr. E. E. Barnard, at the Lick Observ- 



Ttory, on the 20th and 21st inst. The comet is described as faint, 



nd its position and daily motion are given as follows : — 



Local Mean Time, 

 h. m. 

 1895, August 21, II 237 

 Daily Motion 



o 30 



+ 2 i 



1-4. 



Decl. 



+ 53855 



+ 10 



The Latitude VARtATiON Tide. — One of the most interest- 

 ing outcomes of the recognition of the variability of the earth's 

 axis of rotation has been the search for the tide, corresponding 

 to the latitude variation. The separation of the axis of rotation 

 from the axis of figure must cause at any point on the earth's 

 -urface successive divergences of the sea-level, from that which 

 would exist if the figure of the earth remained a fixed ellipsoid 

 of revolution. This consicleration naturally led to the inquiry 

 whether a small oscillation in the mean sea-level could be actually 

 ■detected, bavins; the same ])eriod as the displacement of the 

 pole. The earliest results published were those obtained by 

 Dr. Bakhuyzen (Astr. A'aek. No. 3261), who used the tidal 

 observations for the years 1855 to 1892, registered on a mareo- 

 graph at the Helder, and these results showed a satisfactory 

 agreement with those deduced from astronomical observations. 



In the meantime Mr. A.. S. Christie has been at work on the 

 records made at the United States Coast Survey mareograph 

 stations, and his results, embodied in a paper read before the 

 Philosophical Society of Washington, are now before us. The 

 paper is divided into two sections, the first of which is devoted 

 to the derivation of the formuhv necessar)' for the elimination of 

 the effects of other tides, and the second contains the results of 

 the application of these formul.-e. 



The observations employed are obtained from two series, made 

 at stations in the vicinity of San l-'rancisco, namely, at Fort 

 Point (1856-70) and Sausalito (1877-91). Mr. Christie has 

 also used a similar series made at I'ulpit Harbour, Penobscot 



NO. 1348, VOL. 52] 



Bay, Maine (1870-SS). It will be sufficient to give here the 

 final result arrived at by combining the results at San Francisco 

 and Pulpit Harbour. The period deduced is 431 ±4 days, and 

 the value of the half-range tide is 15 ± 2 mm. ; while the dates 

 at which the critical phases of the tide occurred are : — 



San Francisco. Pulpit Harbour. 



Min. , 1872, July 15 + 15 days ... 1878, .\ugust 22 + 10 days. 

 Max., 1873, Feb. 15 ± 15 ,, ... 1879, March 25 ± 10 ,, 



Dr. Bakhuyren's value of the half-range is 8'2 mm., a result 

 that does not differ greatly from the mean here given, 15 mm., 

 or from either of the two results, 17-4 mm. and I2"5 mm., on 

 which this value rests. 



Reduced to the latitude of Berlin, we have another com- 

 parison between the investigations of the .-Vmerican and Dutch 

 astronomers, and the results are still fairly satisfactory, as shown 

 below : — 



fulian Date of Maximum Latitude of Berlin. 



Bakhuyzen, from astronomical observations 2405 141 Julian 



,, from discussion of Helder tides ... 201 



Christie, from San Francisco tides ... ... 153+16 



It seems possible, therefore, that this difficult question of the 

 motion of the earth's pole may be attacked by two quite separate 

 processes. 



The Solar Parallax from Mars Observatio.vs. — With 

 the view of making a new and trustworthy determination of the 

 solar parallax, a scheme was suggested in 1892 by the authorities 

 of the Washington Observator)' for the observation of the differ- 

 ence of declination at the time of meridian passage between 

 Mars and a number of selected stars. The horizontal equatorial 

 parallax of Mars reached in that year a maximum of 23"'4, a 

 sufficiently favourable condition, though the small altitude of 

 the planet in the northern observatories was likely to introduce 

 considerable uncertainty in the amount of refraction. Among 

 the observatories that replied to the invitation of Washington to 

 take part in this scheme are those of Gotha and the Cape of Good 

 Hope. The result of the combination of the two sets of observations 

 has recently been published by Dr. Paul Harzer, and areof especial 

 interest, since Gotha lies nearly on the northern limit of the 

 region in which observations of Mars could be made with 

 sufficient accuracy. 



It was a part of the original suggestion — to which some ex- 

 ception was taken at the time — that in addition to the method 

 of fixing the declination of the centre of Mars by the employ- 

 ment of a pair of wires, separated by about 16" to cut off equal 

 segments from the northern and southern limbs of the disc, a 

 reflecting prism should be mounted outside the eyepiece, and 

 that half the observations should be made with, and half with- 

 out the use of this additional apparatus. The result of the pre- 

 caution is shown in the following figures, in the case of the two 

 observers who look part in the series : — 



Mars stars 

 Mars 



Dr. H.-uzer. 



+ 0-253 + 0-039 

 -0-270 + 0091 



Dr. Rohrbach. 



-o'3S3+o'i29 

 -o-523±o-262 



These figures imply that Dr. Harzer placed the stars too low 

 and the planet too high with reference to the threads, Dr. 

 Rohrbach, in both cases, too high. 



The observations were continued fi-om June 22 to September 

 23, and when combined in three groups, formed on the assump- 

 tion that the error of the ephemeris is constant throughout each 

 group, the resulting values of the solar parallax are — 



Group 



I. 



IL 



IIL 



IT = 8-680+0081 

 = 8-890+0-089 

 = 8-828+0-065 

 or combined into one, ir = 8"-799+o"-044. 



The complete combination of the whole series formed into 

 20 normal places, and in which the [xjssible variation of the 

 error of the ephemeris is also sought, gives ir =8"'8oo±o"-039, 

 and the value of di is expressed in the form 



rfS 



_ - i"-i47 + o"-28S/ 



where /and A are reckoned from August 7-000, and the unit ''or 

 / is 50 days. 



