Januabt 1, 1897.] 



KNOWLEDGE. 



11 



It should be noted that the features here pointed out 

 are visible on the small areas of the sky shown on the 

 photographs ; areas of about two square degrees, which is 

 about half the photographic field of the twenty-inch 

 reflector. On photographic fields of twelve degrees in 

 diameter, such as have been taken with portrait lenses on 

 a scale about four-thirteenths that of the reflector, are 

 also seen curves and combinations of stars which are not 

 prominently visible on the larger scale. 



The smaller scale shows the stars in closer juxtaposition, 

 and therefore more within the range of the capacity of 

 the eye for grouping them ; and if any distinctly visible 

 group does not exceed one and a half degrees in length, 

 or in diameter, we have reason for inferring that the 

 group is within the influence of gravitation, as the evidence 

 afforded us by the photographs of the great nebula in 

 Andromeda proves. We have no evidence indicating the 

 distance of this nebula from the earth, nor have we any 

 knowledge of the distance of the groups of stars which we 

 are now investigating ; and we have no means for deter- 

 mining the limit of the influence of gravitation. 



Can we, then, discover any cause, or force, now in 

 operation that would enable us to explain, or give a 

 reason, for the grouping of the stars in the manner shown 

 upon these photographs and confirmed by many other 

 photographs which are available for examination ? 



Photographs showing this grouping of the stars have 

 been taken by the Brothers Henry in Paris ; by Dr. Gill 

 at the Cape ; by Mr. Kussell at Sydney ; by Dr. Max 

 Wolf at Heidelberg ; by Von Gothard in Hungary ; by 

 Prof. Pickering and Prof. Barnard in America ; and by 

 others in various parts of the world ; and they all confirm 

 the reality of stellar groupings in the parts of the sky to 

 which they refer. 



What, then, is the explanation suggested to account for 

 these persistent appearances ? Are we to infer that the 

 stars, or many of them, have been evolved out of some 

 attenuated matter in space by the action of vortical motions 

 and by gravitation ? If so, where is the material and 

 whence the source of the vortical motions '? 



Photographs of nebuL^ and the descriptive matter con- 

 cerning them which are requisite to furnish answers to the 

 questions will be given in the next number of Knowledge, 



REPORTS OF OBSERVATORIES. 



AMONG the statements made by the Rev. W. Sid- 

 greaves in his report of observations during the 

 year 1895 at Stonyhurst, we may instance the 

 following : drawings of solar spots and facula^ 

 were made on all convenient days, and in con- 

 nection with these, photographs were taken of the H-K 

 region of the solar spectrum, with the object of observing 

 how closely the double reversals shown by integrated 

 solar light follow the disturbances of the solar surface. A 

 series of photographs of the spectrum of p Lyra' has been 

 taken, and three good plates for each day of the light 

 period have been selected for measurement. A wave-length 

 chart of the spectra of forty-three of the brighter stars 

 has also been made from the photographs obtained with 

 the eight-inch objective. 



Eeports are furnished by Sir Piobert Ball and by Mr. 

 Newall to the Observatory Syndicate. The chief work in 

 progress at the Cambridge Observatory consists of the 

 preparation and publication of two catalogues. In the 

 smaller catalogue about nine thousand stars have been 

 found in former catalogues, and their places have been 

 carefully compared with these, with the result that many 

 instances of proper motion or of error have been detected. 



Mr. Newall has necessarily devoted his attention almost 

 exclusively to the adjustment of the Bruce spectroscope. 

 Photographs have, however, been taken, measured, and 

 discussed of a Auriga, y Cassiopeiffi, Orion stars, and Venus ; 

 the latter with special reference to its rotation period. 



The Savilian Professor furnishes three small tracts, 

 being the reports of the Oxford University Observatory 

 for the years December 19th, 1893— .lune 9th, 1891 ; June 

 9th, 1894— May 25th, 1895 ; and May 25th, 1895— April 

 30th, 1896, respectively. The first two deal principally 

 with the condition of the instruments and buildings of the 

 observatory. 



The chief work of the observatory has been in connec- 

 tion with the astrographic chart. Oat of the one thousand 

 one hundred and eighty plates required of the observatory, 

 seven hundred and fifty-two have been taken, and one 

 hundred and thirty-six plates, including thirty-seven 

 thousand four hundred and four stars, have been measured. 

 Two series of plates of the planets Pallas (two) and Eunomia 

 (fifteen) have been taken during the past year with a 

 special view to determining their parallax. A small factor 

 has been found for Pallas, and the measures of Eunomia 

 are awaiting discussion. 



A larger pamphlet is issued on the state of the Paris 

 Observatory in 1895. Much time has been devoted to the 

 revision of the right ascensions and polar distances of 

 the catalogue of Paris. Such revision had become very 

 necessary, since the catalogue was originally deduced by 

 Le Verrier from a comparison of Bradley's positions with 

 those of the Greenwich catalogue of 1845. These were 

 subsequently corrected by observations made in Paris 

 during the years 1868-1876, but without affecting the 

 proper motions. 



Besides the ordinary routine work of the observatory, 

 which included eleven thousand three hundred and six 

 observations of stars for the catalogue of Lalande, photo- 

 graphs of three hundred and nineteen plates for the cata- 

 fogue series and two plates with three exposures of an 

 hour for the ecliptic chart, measures of eighty-eight 

 plates of the catalogue series, including thirty-six 

 thousand nine hundred and forty-five stars, special 

 researches were undertaken by various members of the 

 staff. With the Grand Cerde Meridien, M. Boquet has 

 deduced, from a combination of twenty-nme direct and 

 fifteen reflexion observations of Polaris, a latitude of 

 48° 50' 11 05", and from analogous observations of 5 Ursse 

 Minoris 48° 50' 10-78". M. Loewy, assisted by M. le 

 Morvan, have taken advantage of every favourable 

 opportunity to complete their series of lunar photographs, 

 though, unfortunately, these occasions were few. Two of 

 the plates, of date 1895, March 5th and 6th, have been 

 sent to M. Weinek for enlargement on paper. A most 

 beautiful reproduction is given as a frontispiece to the 

 report, on the same scale as the original photograph, and 

 bearing the date l^i94, February 14th. Much difficulty 

 has been found in controlling the motion of such a heavy 

 and complicated instrument so as to insure that the 

 displacement of the image on the sensitive plate may 

 not exceed 0'15" or 0'20" in a second of time. It 

 is determined, in consequence, to impart a separate 

 motion to the eyepiece, and, therefore, also to the photo- 

 graphic plate, and M. Loewy is engaged with M. Gautier 

 in devising the best method of doing so. It may be thus 

 possible to take small phases of the moon which require 

 several seconds of exposure. At the request of M. .lanssen, 

 M. Bigourdan has spent his holidays in measuring the 

 weight of Mont Blanc. Observations have been made at 

 Grands Mulcts (three thousand and fifty metres) and at 

 Chamounix (one thousand and fifty metres) ; those from 



