Fbbeuaey 21, 1902.] 



SCIENCE. 



289 



the instrument, respectively. Strains in 

 tlie supporting cradle cannot induce 

 strains in the spectrograph. The old 

 method of supporting spectrographs en- 

 tirely from one end, allowing the other end 

 to project unsupported out into space, in- 

 vites flexure effects, and it is hoped that 

 the new method of support will prove to be 

 a radical improvement. The whole spec- 

 trograph Avill be moved to bring the slit 

 into the focus of the Cassegrain telescope. 

 A temperature case similar to the one used 

 for the past three years on the original 

 Mills spectrograph will enclose the instru- 

 ment. 



On the Capture of Comets by Jupiter: 



Peecival Lowell. 



This paper gave in diagrams a part of 

 the author's memoir on the subject, not yet 

 published, in which he explained the action 

 of Jupiter upon a comet entering the 

 planet's sphere of activity, and the relation 

 borne by the direction and the speed of 

 approach to the comet's subsequent be- 

 havior. The paper showed that Jupiter 

 was not only capable of transforming at 

 one encounter a parabolic comet into an 

 elliptic one of about half his own major 

 axis, but could actually cause a comet to 

 make the planet instead of the sun the goal 

 of its visit, and send it back again into 

 space without circumnavigating the sun at 

 all. The argument then developed a critic- 

 al angle differentiating those comets 

 which Jupiter's action might render retro- 

 grade from such as it could not. A table 

 here showed that the angle of approach of 

 each of the comets composing Jupiter's 

 comet family not only at the present 

 moment fell within the critical angle for 

 each, but must do so for all time, abstrac- 

 tion made of perturbations by other bodies 

 and the approximation being of the first 

 order. In other words, that under these 

 conditions the present direct motion of all 



the members of Jupiter's comet family was 

 such in perpetuity. The planet might 

 drive them off into space but could never 

 render any of them retrograde. 



Tlie Latitude-Variation Observatory of 

 the International Geodetic Association: 

 Herman S. Davis. 



A brief statement of the plan of the 

 International Association in the establish- 

 ment of the four stations at Gaithersburg, 

 Maryland, Ukiah, California, and in 

 Japan and Sardinia for a systematic and 

 continuous series of observations for the 

 study of variations of latitude. Particular 

 attention was given to the two stations in 

 the United States under the general direc- 

 tion of the Coast and Geodetic Suiwey, the 

 one in charge of Dr. Schlesinger, at Ukiah, 

 and the other in charge of the speaker, at 

 Gaithersburg. Illustrations Avith the lan- 

 tern were shown of both these stations with 

 plans of the buildings and views of the 

 telescope at Gaithersburg. Attention was 

 called to the admirable quality of the ob- 

 servations made by Mr. Edwin Smith, who 

 was in charge of the station at Gaithers- 

 burg prior to January, 1901, and entire 

 credit given him for the erection of the 

 buildings and installation of the instru- 

 ments at this station, and to the active and 

 enthusiastic support of the superintendent 

 of the Coast Survey from the very incep- 

 tion of the plan to establish these stations 

 in the United States. 



' Some Vices and Devices in Astronomical 

 Computations: Herman S. Davis. 

 Owing to the briefness of the time re- 

 quested for the presentation of this paper 

 and the fact that a considerable portion of 

 that time was devoted to the preceding 

 paper which was presented by request— not 

 being regularly on the program— the 

 speaker gave only a meager description of 

 some of the methods which he is now using 

 in the new reduction of the 160,000 star- 



