SCIENCE. 



317 



SCIENCE : 



A Weekly Record of Scientific 

 Progress. 



JOHN MICHELS, Editor. 



Published at 



TRIBUNE BUILDING, NEW YORK. 



P. O. BOX 383S. 



SATURDAY, JULY 9, 1881. 



OBSERVATIONS UPON THE COMET AT 

 PRINCETON. 



The comet has been seen and observed every night 

 since June 25, except on June 30th. Every night, 

 however, except July 2d and 3d, the observations 

 have been interfered with by clouds, so that very little 

 continuous thoroughly satisfactory work has been pos- 

 sible. 



The light has fallen off rapidly. On the 26th, the 

 comet was for half an hour better seen than at any 

 other time, and the nucleus was judged to be just 

 about equal to Arcturus in brilliancy. On July 2d, 

 it was compared pretty carefully with the Pole Star 

 and with a Urs. Majoris by squinting, so that the 

 blurred images of star and comet were brought close 

 alongside. I judged it just equal to Polaris and about 

 \ to \ of a magnitude fainter than Dubhe. 



The nucleus and coma have presented a very inter- 

 esting series of telescopic phenomena, in the main 

 such as have been seen in all other large comets. It 

 is noteworthy, however, that immediately behind the 

 nucleus no strongly marked dark shadow-like stripe 

 has been developed, nor, what is perhaps just as com- 

 mon 011 the contrary, any bright central streamer. 

 On the whole, the central portion of the tail has been 

 a little less brilliant than the edges, even close to the 

 head, but the difference has been slight. On the 25 th, 

 the nucleus about 10 P. M. showed 5 projecting jets, 

 much like the pseudopodia of some low animal organ- 

 ism — not well formed, nor distinct, nor symmetrical, — 

 their length from two to six times the diameter of the 

 nucleus, those on the front of the nucleus being the 

 longer. 



On the 26th, the nucleus was almost entirely sur- 

 rounded with a nearly complete, well defined, circular 

 envelope about i' in diameter. In this envelope was 



a curious oval vacuole, behind the nucleus, but on the 

 preceding side of the axis of the tail. 



On subsequent evenings no envelopes nearly so 

 complete were noted — only jets of varying length and 

 position, those on the side of the sun being apparently 

 blown back, like flowing hair, by some solar repulsion. 



On the 29th there was but one jet on the sunward 

 side, and this was curiously curved toward the preced- 

 ing side, making the whole look like a comma. (We 

 use preceding rather than Western, because below the 

 the pole where the comet was, the terms Eastern and 

 Western might lead to misapprehension.) 



On July 1st the head was curiously unsymmetrical. 

 The coma was extended out in the South following 

 direction like a great liberty cap, the axis of the prin- 

 cipal jet which divided both ways, in front like hair 

 parted in the middle, being inclined some 50 to the 

 line of this extension. 



With the spectroscope a number of observations 

 have been made. 



The nucleus has generally given a simply continu- 

 ous spectrum, extending from below C well above G ; 

 but on June 25th and July 1st, it showed distinct band- 

 ing at points where the bands of the spectrum of the 

 coma crossed it. 



This was seen by several observers on the 25th, and 

 by both Mr. McNeill and myself on the 1st. 



The spectra of some of the brighter jets had been 

 caught and isolated several times. They were in ail 

 cases continuous, without detectable bands of any 

 kind. 



The spectrum of the tail was found to be continu- 

 ous, with a faint superposed band-spectrum, the same 

 as that of the coma. On July 1st and 2d this band- 

 spectrum was distinctly traceable to at least 15' dis- 

 tance from the head of the comet, the continuous 

 spectrum perhaps 5' or 10' further. 



The spectrum of the coma consisted of the usual 

 three bands ; but both the upper and lower bands, 

 though pretty bright, were very ill defined; so much 

 so, that I could obtain no satisfactory measurements of 

 wave length, farther than to observe on June 25 th and 

 26th, that the lower edges of the upper and lower 

 bands of the so-called ' first ' spectrum of Carbon, (2,, 

 5635 and 4740) given by a Bunsen burner, fell appa- 

 rently near the lower limit of these two bands in the 

 comet spectrum as seen with a one prism spectrum. 

 But these comet-bands did not look at all like the 

 flame bands, the difference of appearance being so 

 great, as somewhat to shake my belief for the time 

 being, in the identity of the two spectra. 



The middle band, on the contrary, was perfectly de- 

 fined at its lower edge, and with the one prism spect- 

 roscope distinctly showed three fine lines in the band, 

 and these, so far as could be judged, coincided exactly 



