280 



(SCIENCE. 



IVoi.. II.. No. :!0. 



PROCEEDINGS OF SECTION A. — MATHEMATICS AND ASTRONOMY. 



PAPERS READ BEFORE SECTION A. 



^Coviinued-l 



Orbit of the great comet of 1882. 



BY EDGAR FIUSBIE OF AVASHII^GTOX, DC. 



This is a partial record of observations at Wash- 

 ington. Mr. VVinloclc is preparing a description of all 

 the physical phenomena of the comet vifhicli were 

 there observed. The first Washington observation 

 of the comet was at two o'clock on a September 

 afternoon, and a comparison was. then made with 

 the position of the sun. Good observations were ob- 

 tained on the meridian for three days. The calcula-- 

 tions from these served to fix the place of the comet 

 with fair appro.\iraate accuracy for three months, 

 which was a somewhat remarkable success. After- 

 ward a difficulty occnrred in obtaining accurate ob- 

 servations; because there" were several different points 

 of light presented ia an ill-defined nucleus, and it 

 was uncertain whether the observations always re- 

 ferred to the same luminous point. These observa- 

 tions were made in October and November. The fol- 

 lowing ephenieris was calculated : ^- 



Sept. 17.22S2 89° 13' 42.70" 



n 34C° 1' 7.91" log. a 1.9331:566 



jr 69 36 12.79 Jog. q 7.8904739 



i 141 59 52.16 period 793.689 



The author compared the foregoing with the obser- 

 vations of other astronomers. The most prominent 

 variation was in resi^ect to the period, which others 

 gave as 659, 997, 852, and 654 years. A contrivance 

 was exhibited, showing the respective positions of 

 the earth and comet, and their directions of motion, 

 by means of pasteboard planes attached at an angle. 



The rotation of domes. 



BY G. W. HOtTGH OF CHICAGO, ILL. 



Obskuvatort domes are iii general very heavy. 

 As they grow old. owing to the settling of walls and 

 other changes, they are apt to hecome almost un- 



manageable. The dome at Chicago is very weighty, 

 every thing about the observatory being built in a 

 very substantial manner. When Dr. Hough first 

 tried to move the dome, he found its two sides work- 

 ing with unequal friclion; and this was afterward 

 remedied to some extent, but by no means fully. 

 About two months ago a gas-engine was placed in 

 position to revolve the dome. It was agre.at satisfac- 

 tion to see the dome go round continuously, without 

 hitches. The cost of moving the dome by such 

 means is a mere trifle, aside from the first cost of 

 the engine. The use of water-power where that was 

 easily accessible mxist, however, be preferred in many 

 instances where a sufficient head is supplied by street 

 mains. 



Dr. C. A. Young said, in discussing the foregoing, 

 that when he came to Princeton he found a very heavy 

 dome there. One man, using thirty pounds pressure 

 on a two-foot crank, was veiy tired after giving the 

 dome one turn. A gas-engine has since been put in 

 below, and the power is communicated by a belt. A 

 revolution can be made in four minutes, and the 

 shutter raised in two. In general, tlie dome is placed 

 and the shutter opened wilhia five minutes. Dr. 

 Young expressed a liope that the Brush storage bat- 

 teries would furnish electrical illumination and power 

 for the woi'k of observatories, as the electricity might 

 be slored even from a gas-engine operating a dynamo 

 during hours of the day when there was no other use 

 for its power. At present the direct action of a gas- 

 engine on a dynamo, with no intervention between 

 the dynamo and the light, was too irregular to serve 

 the purpose. 



Descriptive-geometrical treatment of surfaces 

 of the second degree. 



BY J. BUKKITT WEBB OF ITHACA, N.Y. 



Fon the purpose of greater conciseness the speaker 

 confined his remarks to the general ellipsoid, remark- 

 ing that the usti.al treatment of problems upon this 

 surface — as, for instance, such problems as finding 

 the shade and shndow, or drawing tangent planes — 

 is lacking in generality ; the body being taken in such 



