134 



KNOWLEDGE, 



[Juke 1, 1898. 



probable that occuUatione of stars as faint as the ninth 

 magnitude can be observed photographically. 



Measures were next made of the intensity of the last five 

 images of 26 Arietis, to see if there was any diminution in 

 light due to the absorption of a lunar atmosphere. The 

 distances of these images from the moon's limb were 1-8 ", 

 I'i", 1-0", O'C", and 0-2", respectively. The corresponding 

 changes in light expressed in magnitudes as compared with 

 ten more distant images were +003, +0-03, —0-02, 

 + 008, and — 0-02. A positive sign denotes that an image 

 was fainter than those at a greater distance from the 

 moon. From this it appears that no diminution in light 

 was perceptible. No correction need be applied to any of 

 the above calculations for the diameter of the star's disc, 

 since, assuming its intrinsic brightness equal to that of the 

 sun, its time of disappearance would be only 0-002s. [Proc. 

 Anwr. Acad., XVI., p. 1. 



In this connection it is interesting to note that the 

 determination photographically of the position of the moon 

 by means of a star about to be occulted, was one of the 

 subjects investigated by Prof. G. P. Bond forty years 

 ago. He obtained a number of photographs of the moon 

 and a Virginis shortly before the occultation of the latter 

 on June 2nd, 1857. 



A VARIABLE BRIGHT HYDROGEN LINE. 

 The presence of the bright hydrogen line H^ in the 

 spectrum of the star A. G. C. 9181 was found from the 

 Draper Memorial photographs in 1895, and was announced 

 in the Astrojihi/xical Journal, Vol. I., p. 411. From a 

 comparison of photographs of this object taken on different 

 dates Miss A. J. Cannon finds that this line is variable. 

 On October 5th, 18!i2, it was invisible. On November 28th, 

 1894, it was about half as bright as the corresponding line 

 in A. (i. C. 9198, uj Canis Majoris. On April 27th and 

 30th, 1895, the line in A. G. C. 9181 was distinctly the 

 brighter of the two, while in January, 1897, it was again 

 invisible. From a large number of photographs of this 

 object taken recently it appears that this line, which was 

 bright in October, 1897, is now, December 27th, invisible. 



A NEW SPECTROSCOPIC BINARY. 



From an examination of the Draper Memorial photo- 

 graphs Mrs. Fleming finds that the star A. G. C. 20203, 

 fi Lupi, is a spectroscopic binary. The period has not yet 

 been determined, but photographs are being taken for this 

 purpose. 



Measures of the spectroscopic binaries, jw.' Scorpii and 

 A. G. C. 10534, show that the relative velocities of the 

 components are approximately 460 km. and 610 km. 

 respectively. The velocities are therefore much greater 

 than in the case of ? Urs.T Majoris and /3 Aurigrc. The 

 separation of some of the lines amounts to as much as 

 nine tenth-metres. 



PHOTOGRAPHIC SPECTRUM OF THE AURORA. 

 Various attempts have been made at this observatory to 

 photograph the spectrum of the aurora. In 1880 on several 

 occasions long exposures were given to plates during bright 

 auroras, but no result was obtained. On April 1, 1897, 

 Mr. Edward S. King succeeded in obtaining a photograph 

 in which four bright lines were visible, but imcertainty 

 existed regarding their wave lengths. The exposure was 

 one hundred and forty-seven minutes. During the bright 

 aurora of March 15th, 1898, he obtained a photograph 

 showing two bright lines. The exposure was one hundred 

 and forty-one minutes. The brightest of these lines extends 

 in wave length from about 3892 to 3925, and the wave length 

 of the second is 4285. Assuming the two brighter lines 



photographed in 1897 to be identical with these, the four 

 lines on that plate have the wave lengths 3862, 8922, 

 4288, and 4094. The first of these lines is very faint. 



The errors of measurement of these lines do not exceed 

 one or two units, but much greater uncertainty exists in 

 the reduction owing to difliculties in comparing them with 

 the lines of the solar spectrum, which was photographed 

 upon the same plate. Probably the two auroras gave 

 difi'erent spectra. That in 1897 was taken with a wide 

 slit, but the images of the lines were well defined on the 

 edges and of equal width, so that the line 3922 was 

 probably really narrow and coincident with the edge of 

 ^greater wave length of the line 3892 to 3925. The 

 spectroscope used was not especially designed for photo- 

 graphing faint surfaces, and it is hoped that better results 

 may be obtained with a new instrument now in course of 

 construction. As is the case with all results announced 

 in these circulars, it is expected that full details will be 

 published later in the annals of the observatory. 

 Harvard College Observatory. Edwabd C. Pickebdco. 



Notf»0 of ISoolts. 



The Smithsonian Institution, 1^40-1890 : the Histor;/ af its 

 First IJalf-Century, Edited by George Brown Good. (City 

 of Washington.) When James Smithson, in 1826, drew 

 up his will [containing this most significant provision, " I 

 bequeath the whole of my property to found at Washington, 

 under the name of the Smithsonian Institution, an estab- 

 lishment for the increase and diffusion of knowledge among 

 men," he laid the foundation of an organization which, 

 for half a century, has been one of the most important 

 agencies in furthering the intellectual development of man- 

 kind. The institution is a rallying point for workers in 

 every department of scientific and educational activity, and 

 the chief agency for the free distribution of books, apparatus 

 of research, and of scientific intelligence throughout the 

 world. Its pubUcations, which include some hundreds of 

 volumes, are sent to all the most important libraries in the 

 world, and many of them, it is safe to say, are found on 

 the work-table of every scientific investigator. In view of 

 the present enthusiasm for the idea of the federation of the 

 Anglo-Saxon races, it may not be inopportune to point out 

 that James Smithson was an Englishman who graduated 

 at Oxford in 1786. "The best blood of England flows in 

 my veins," he once wrote ; " on my father's side I am a 

 Northumberland, on my mother's I am related to kings." 

 This sumptuous volume contains a complete history of the 

 Institution, and appreciative notices (each by a distinguished 

 man of science) of the various branches of work carried out 

 under its auspices during its existence. Though the plan 

 of the volume is due to the late Dr. Goode, the enormous 

 labour involved in seeing the work through the press has 

 fallen upon Prof. S. P. Langley, the present secretary of 

 the Institution, whose own contributions to science have 

 placed him in the foremost rank among investigators of 

 natural phenomena. The volume is in every way a worthy 

 jubilee memorial ; the printing, the plates- — in fact, the 

 whole /on/(a; — leave nothing to be desired ; and whoever is 

 fortunate enough to obtain a copy may well be gratified at 

 his possession. 



Memorials of William Cramh Bond and of his timi George 

 Phillips Bond. By Edward S. Holden. (1897. Ban 

 Francisco, C. A. Murdock & Co. ; New York City, Lenicke 

 Buechner.) It is not given to every man to be a 

 Boswell, but the pity of it is that would-be Boswells do 

 not recognize the fact, and assume the rule. The first 

 part of this book is extremely dull. It consists largely of 



