July 30, 1896] 



NA TURE 



301 



three Grass Snakes (Cyclopkis vernalis), a Hog-nosed Snake 

 (Heterodon plalyrhinos) from Montreal, received in exchange ; 

 two Patagonian Cavies {Dolichotis patachonica), two Ypecaha 

 Rails {Aramidts ypecaha), bred in the Gardens. 



OUR ASTRONOMICAL COLUMN. 



November Meteors. — With the July number of Monthly 

 Notices R.A.S. a circular is issued by G. Johnstone Stoney, 

 calling the attention of astronomers to the approach of the great 

 secular maximum of the Leonids, which is due about 1S99 or 

 1900. It is probable that this swarm was drawn into the solar 

 system by the planet Uranus about February or March a.d. 126, 

 and carelul observations during the next few years may furnish 

 materials for confirming or rejecting this hypothesis. Photo- 

 graphy should be employed as widely as possible, and wherever 

 practicable the time of appearance of each meteor recorded. 

 Accurate simultaneous observations from diflerent stations will 

 be of exceptional use. The radiant-points and times of appari- 

 tion of all meteors should be exactly noted, commencing a few 

 nights before, and continuing some nights after, November 14 

 and 15. 



Plumb-line Deviations. — M. Messerschmitt, who has 

 been for some time engaged in the determination of latitude 

 and azimuths of a series of points in the Swiss Triangula- 

 tion, has communicated (Ast. Nack., No. 3365) the results of 

 his most recent investigations. It may be recalled that M. 

 Messerschmitt's first determinations were made in West Switzer- 

 land, and these were followed by further researches in the north 

 of the country, which corroborated his previous results. The 

 present paper is concerned with observations made on a line 

 drawn approximately north and south through the centre. 

 Collecting his results into a table showing the difference between 

 geodetic and astronomical latitude, and arranged in order of 

 increasing distance from the equator, a systematic deviation from 

 the vertical is clearly shown. In the midst of the mountains 

 (around Andermatt for example) these deviations are quite small. 

 Going south they increase rapidly, and attain a negative maximum 

 of 20" (astronomical — geodetic) towards Lugano. A positive 

 maximum occurs about Goschenen, the entrance to theGotthard 

 Tunnel ; and still further north, the difference diminishes again, 

 and changes sign about the latitude of ZUrich. Schaffhausen 

 shows again the position of negative maximum. The position 

 of the mountain chains generally explains these variations. 



An investigation, founded on these deviations of the plumb- 

 line, of the form of the surface of the earth for a meridian length 

 of about 200 km. through the Gotthard district, discloses the 

 fact that the ellipsoid sinks everywhere below the geoid. 

 Selecting as a zero point that position where no deviation from 

 the vertical exists (47°'I 15' lat. ), the greatest difference between 

 the two surfaces occurs near Airolo (the southern exit of the 

 tunnel), where it amounts to nearly five metres. Going south- 

 wards from this point the surface sinks gradually, and approaches 

 the ellipsoid before the valley of the Po is reached. 



The Hamburg Observatory. — Prof. Rumker's report of 

 the observatory work during the year 1S95, shows that the 

 activity of the various departments is fully maintained. The 

 observations with the equatorial have mainly consisted in 

 deriving the positions of small planets and comets, and of the 

 fainter stars with which the nebula;, whose places have been 

 published in a communication from the observatory, have been 

 compared. With smaller instruments attention has been given 

 by Dr. H'anig to variable stars and occultations by the moon. 

 With the meridian instrument, in addition to observations re- 

 quired for the accurate distribution of time signals, arrangements 

 have been made for observing stars in the degree 80-81 N. 

 Decln. down to 9*3 mag. In addition to this varied work, the 

 attention of the staff has been called by Dr. Auwers and others 

 to discrepancies between the places of stars in the Hamburg 

 catalogue, and those recently obtained in the " Astronomischen 

 Gesellschaft " zone catalogue. This has necessitated much search- 

 ing of old records, and in some cases the detection of errors, 

 which will be published in a communication from the observatory. 



The Du.nsink Observatory.— The seventh part of the 

 astronomical observations and researches made at Dunsink, and 

 published under the direction of Prof Rambaut, contains the 

 meridian places of 717 stars, of which upwards of 2000 observa- 



NO. 1 396, VOL. 54] 



tions have been made. These stars have been selected on 

 account of suspected large proper motions, and the observations, 

 interrupted as they have been from several causes, have been 

 spread over eleven years. But, nevertheless, the accuracy main- 

 tained throughout is of a very high degree. From an examina- 

 tion of the separate results, the probable errors in R. A. and 

 Declination are, respectively, + o"'037, and ±o"'5o5. This 

 error is probably increased by the uncertainty of the proper 

 motion in many cases, and does not fully express the accuracy of 

 the work. The Pistor and Martin's meridian circle, with which 

 the observations have been made, has been frequently reversed 

 in the course of the work, and the determination of latitude, on 

 which great care has been bestowed, is slightly different in 

 the two positions. With Clamp West the resulting latitude is 

 53° 23' I3"'05, and with Clamp East three-tenths of a second 

 less. The value used in the final reduction is 53° 23' i3"'oo, 

 and the results, it is believed, coincide very closely with Auwers' 

 fundamental system. The cause of this systematic difference in 

 the latitude, however, has not been satisfactorily explained. 



Obser\-atory of Moscow. — The last issue of the Annals 

 of this Observatory (series 2, vol. iii. part 2, 1896) contains 

 several papers of general interest. The director, W. Ceraski, 

 contributes the following articles : (l) " Photometry of the star 

 cluster X Persei," in which he gives the measures of the magni- 

 tude of seventy stars of the group, determined with a ZoUner 

 photometer on a lo-inch refractor. One star he finds to be 

 variable, and recommends its further study. (2) "Observations 

 of eclipses of Jupiter's satellites without photometric ap- 

 pliances," using eye estimates of relative magnitude compared 

 with some neighbouring star of known brightness. (3) "On 

 the temperature of the sun," in which he gives the inferior 

 limit to be about 3500° C. (4) "A new method for the 

 electrical comparison of pendulums." — P. Sternberg discusses 

 the photographs he obtained during the transit of Mercury on 

 May 9, 1891, and also contributes an important description of 

 his determination of the variation of latitude at Moscow'. — B. 

 Modeston gives a full description of the calculation of double- 

 star orbits by the methods of Kowalski and Encke respectively. 

 — S. Blajko, as the result of thirteen photometric me.asures of the 

 magnitude of Mira Ceti during the winter of 1S94-5, finds 

 evidence of a secondary maximum in its light curve, occurring 

 about a month previous to the highest maximum, the magnitudes 

 at the secondary and principal maxima being about 3'5 and 3'l6 

 respectively. 



THE SOLAR ECLIPSE OF APRIL 16, 1893. 



Ayr DESLANDRES has now issued his report on the work 

 ■'-'■'• ■ accomplished by the French expedition to Fundium, Sene- 

 gambia, for observations of the total solar eclipse of April 16, 

 1893. Some of the results obtained have already been made 

 known, and these are now brought into connected order and 

 discussed. A full account is also given of the general objects 

 and organisation of the expedition. The programme decided 

 upon included the photography of the corona, a photographic 

 study of the coronal spectrum, especially in the ultra-violet, 

 and a spectroscopic study of the movements of the corona. 



The report is of special importance in view of the approaching 

 eclipse, for the reason that reference is made to several points 

 which may serve as a guide in future operations. For example, 

 M. Deslandres' experience indicates that for the corona pictures 

 plates of moderate sensitiveness give better results than the 

 plates of greater rapidity. Another practical suggestion is that 

 at least two cameras should always be employed in the search 

 for an intra-mercurial planet ; M. Deslandres found it impos- 

 sible to determine whether certain spots on the single plate 

 which he obtained represented stars or photographic defects. 



The general results relating to the coronal spectrum are thus 

 stated: (i) The continuous spectrum of the corona, which 

 forms the greater part of its light, is most intense on the red 

 side, relatively to the spectrum of the disc, and the difference 

 appears to become greater as the point considered is further 

 removed from the photosphere. (2) The spectrum of dark lines, 

 under very favourable conditions, did not appear at 5' from the 

 sun's limb ; at this height the light diffused by the coronal 

 particles is still too feeble with respect to their own light. (3) 

 The luminous gases of the corona, indicated by the fine lines, 

 have not the same intensity or composition in different parts of 



