236 



SCIENCE. 



questions on this point, and we would be obliged if any 

 of our correspondents would furnish a few facts. We 

 understand that some makers make use of a very soft 

 glass, the surface of which becomes defaced in a short 

 time : a dealer calls this " spongy glass." We would like 

 to know where the respective makers purchase glass 

 for objectives, and its composition. 



ASTRONOMY. 

 COMET (£) 1 88 1. 

 Prof. Barnard, of Nashville, Tenn., announces the 

 discovery of a comet on the morning of May 12, 1 881, in 

 R. A. 22 1 ' 59"' 18 s , dec. + 14° 24' 30". An observation 

 on the following day gave R. A. 22'' 58 1 " 52 s , dec. + 14 

 36 o , thus indicating a motion 24 s in R. A., and 11 in 

 Dec. The comet is reported as very faint. 



ON THE USE OF THE ELECTRIC TELEGRAPH DURING 

 TOTAL SOLAR ECLIPSES.* 



If we suppose a single observer to be prepared for the 

 observation of all the total solar eclipses of a century, we 

 shall find that the entire amount of time during which 

 he may contemplate the totally eclipsed sun will not dif- 

 fer much from an hour. We may be sure then of the 

 expediency of any scheme whereby the rare moments 

 of these eclipses may be utilized to their utmost ex- 

 tent. If such scheme is devised, two impor.ant results 

 are likely to follow. 



(1.) Economy of the sum-total of energy in any 

 particular line of solar research. 



(2.) A consequent enlargement of the means of re- 

 search in other directions. 



The general conception of ihe scheme proposed in 

 this paper may be very briefly stated : Suppose a station 

 to the east and a station to the west on the line of 

 any total eclipse, as widely separated as practicable, 

 and equipped for similar observations of discovery dur- 

 ing the progress of the eclipse ; the method proposes 

 the electro-teiegraphic transmission of important observa- 

 tions made at the western station to observers at the 

 eastern station, with due speed for their verification or 

 rejection when the lunar shadow reaches the latter 

 station. 



For illustration, consider the next total echpse, — that 

 of 1882, May 16. In detail, the particular advantages 

 in connection with this eclipse seem to be about these : 



(1.) The path of totality is almost exclusively on 

 land. Central eclipse begins in West Africa ; the line 

 of totality passes to the north-east, crossing Upper 

 Egypt and ihe Nile at El-Akhmym ; thence over the Red 

 Sea, crossing the Tigris a few miles to the south of 

 Bagdad ; then passing a little to the south of Teheran, 

 it traverses Central Asia, and leaves the Asiatic Conti- 

 nent somewhat to the north of Shanghai. 



(2 ) Though not generally through the inhabited 

 regions of the globe, the path of totality lies through 

 several inhabited regions which are widely separate, 

 viz : Egypt near the Nile, Central Persia and Eastern 

 China. 



(3.) These regions are inter-connected by telegraphic 

 cables and land-lines. 



Now, we will suppose that an important observation 

 of discovery is made at El-Akhmym, — an observation 

 of an intra-mercutial planet for example. Between 40 

 and 45 minutes of absolute time elapse before totality 

 comes on at Teheran. During this interval the observer 

 at El-Akhmym will have an abundance of time for 

 transcribing che apparent magnitude and the precise 

 position of the new body, and transmitting the same to 

 his fellow-observer at Teheran several minutes before the 

 lunar shadow reaches him. The latter observer will 



♦Abstract of a paper by D. P. Todd, M. A., presented before the 

 American Academy of Arts and Sciences, Jan. 12, 1881. 



! then have leisure to proceed with the setting of his 

 I circles, the verification of their readings, and the pointing 

 I of his instrument to the precise part of the heavens 

 indicated. He may then be able to see the suspected 

 j object before the eclipse becomes total. He may also 

 decide upon a neighboring star for comparison with the 

 planet, and thus obtain a veiy accurate determination of 

 its position. The observer at Teheran should also be 

 prepared for an independent search for the suspected 

 planet, in the event of receiving a negative message from 

 the observer at El-Akhmym. 



The observation at El-Akhmym should also be trans- 

 mitted to Shanghai, (reached by the shadow more than 

 1 two hours after totality at Teheian), for independent 

 i verification at that point. We might thus observe the 

 I result of nearly three hours' motion of the planet, — 

 I which we might reasonably expect to give important 

 data in regard to its orbit about the sun. Of course, 

 the result of observation at Teheran would also be trans- 

 milted to the observer at Shanghai. 



It was my intention primarily to have considered the 

 total eclipse of 1882 merely as an illustration of the 

 method proposed. Further investigation, however, seems 

 to show that it is at least one of the two most favorable 

 eclipses during the present decade, if not during the 

 present century. 

 Washington, May 18, 1881. W. C. W. 



Comet {b), 1881, Barnard. 



To the Editor of " SCIENCE :" 



On the morning of the 1 2th, while sweeping the eastern 

 sky in search of comets, at about three o'clock, an object 

 entered the field of my telescope which I strongly sus- 

 pected was a comet, as I did not know of any nebula near 

 its place. I at once secured its position relative to a 

 Pegasi, it being in the field with that star. Its position 

 at seven minutes past three o'clock was : 



R. A. 22 h 59 m 18 s 

 Decl. + i4 Q 24' 29" 



The object was watched at intervals until about four 

 o'clock, when daylight prevented further observation. 

 During this time no motion was detected. Wishing to 

 confirm the discovery by a second observation, before an- 

 nouncing it, I waited until the following morning, when 

 upon turning my telescope to the point where the object 

 was seen, I found it had disappeared. 



No doubt now remained in my mind of its cometary 

 character. I began a search to re-discover it. After 

 sweeping for some time in the immediate neighborhood, 

 I found it again as day-light was whitening the sky. It 

 was very close north following « Pegasi. The object was 

 then only visible when the bright star was ob- 

 scured by a part of the ring suspended in my eye-piece. 

 It followed the star by six seconds and was therefore in 

 R. A. 22 h 58'" 52 s . I estimated the difference of declina- 

 tion between comet and star, and found it to be in north 

 declination 14" 36'. No doubt now remaining that it was 

 a comet I telegraphed its position to Professor Swift, Di- 

 rector of the Warner Observatory at Rochester. On the 

 morning of the 14th I again began a search as soon as 

 the object had risen above the horizon, but it could not 

 be found. At first I attributed my not finding it to its 

 low altitude and the bright moonlight. The search was 

 continued until daylight, and I was deeply mortified at 

 not finding any trace of the object. In the morning tele- 

 grams from Rochester and Boston announced failure to 

 find it at those places. 



A short search this morning, when the sky had cleared, 

 at about day-light, resulted no better than yesterday morn- 

 ing. The object on the 12th was slightly smaller than 

 Swift's last comet, which I had been observing on the 

 nth, and was probably a little brighter. On the 13th it 



