Tribune Extras Pamphlet Seria. 



When those three envelopes were formed, that 

 v. as the time when the comet, as seen in America, had 

 three tails. It seemed as though the three envelopes 

 each of them gave the material when a tall 

 was to be formed. And we are led in that way to an 

 explanation of another comet, a very well-known comet, 

 the six-tailed comet of 1744. This was called the six- 

 1 ailed comet ; but it seems to me that when we view the 

 matter in the way we have been considering it we should 

 look upon that comet as a three-tailed comet, not a six- 

 taili-d. You will see clearly iu a rnoinjut that there is 

 pood reason for redueiug the number of tails. 



A comet auch as the comet of 1811 has around its 

 Lead an envelope formed, and from either side of the 

 envelope there is a bright streak, with a dark space 

 behind the head of tho comet. We don't call a comet 

 auch as that a two-tar*p<loomet ; we say It is a one-tailed 

 comet, with the sides of the tail exceptionally bright. 

 If we call that tail, where there are two bright 

 treuks, a single tail, I think we should call this tail 

 where there are six bright streaks a three-tailed comet. 

 tVe should regard the two outer streaks as the outer 

 atrcnks of the tail, the two next as tha outer 

 aide of tho second tail, inside the first, proceeding 

 from an inner envelope as in this case, and the 

 two iusido streaks as the sides ot the third tail. That 

 seems to be the more natural explanation of the matter. 

 And then wo remember what we are so apt to forget, 

 that comets have three dimensions, that they are not 

 merely dis.pl.it ed before us as a picture, with length and 

 bn-adth.but they have thickness also. If you view 

 them from any part they would present the same ap- 

 pearance. That six-tailed comet is really a three-tailed 

 comet, with one tail inside the other, and doubtless it 

 bad three envelopes around the head, and from these 

 envelopes were streaming away those tails another 

 proof of thi.s wonderful repulsive acLuin. 



GREAT COMF-T OF 1811. 



Now, if we consider ilie a-pei-i of the hend nf Dunati's 

 comet, we shall reemrnize Komr.'hing of tho solar action 

 by \\liicli tin' In ad ami tail are formed. H-TO [referring 

 *t> the chari 1 Is the heail of tlie eiuni-t. II"ro you recog- 

 nize tin- different envelopes, connected one with another 

 by brlKht streaks, and you cau perceive that from thea 



envelopes appear streaks of bright mutter swept aw-y 

 on either side of the head. In tho other picture, taken at 

 a later time, the two streaks are distinct, one from an* 

 other. Here Is a wonderful process, and remember the 

 scale on which it is going on. Dr. Holmes spo^e with 

 poetic license of ten million cubic miles of head of thac 

 comet, and ton million leagues of tail : the tail was many 

 times as larsro as Dr. Ilolines'a numbers. 



I must briefly touch on tho theory of Dr. Tyndall, and 

 It is well worthy of attention. Dr. Tyndall went 

 through this experiment : Ho had a long tube, ap- 

 parently ciear of all material substance except air, a-)- 

 sumed to be pure air, and what happened 1 He allowed 

 a small quuntitv of vapor to pass into it 

 by taking a small piece of blotting paper, im- 

 mersed m wnter, allowed to dry, and then 

 put into tho tube, and merely letting the air pass 

 upon it. It seemed as if nothing was carfie'J in, yet 

 when the light from the electric spark w.ts let into it ;t 

 cloud made its appearauee. Ho opened the tube, and 

 swept everything away except an invisible residua. Tho 

 light from the electric spark was nuirln to suiup upon it 

 again, and tho cloud again was formed, so that Dr. Tyn- 

 dall said he had an exact analogue of 

 the tail of the comet, and he considered 

 that the head of the coiner, depriving the solar rays of 

 heating power by not allowing tha heat to pass through, 

 left the actinic power of tho rays in the matter behind 

 the head of the comet, bringing down out of space 

 clouds formed in matter not belonging to the comet, but 

 brought down as tlie comet's tail; and Dr. Tyndall con- 

 siders that he can represent not merely tho formation 

 of a cornel's tail, but all the appearances presented by 

 the head of even Donati's complicated comet. 



CONNECTION OF METEORS WITH COMETS. 



I pass from these facts, wonderful as they are, and 

 introduce the subject of meteors. For a long timo 

 meteors were looked on as phenomena of our atmos- 

 phere, but facts began o be observed which led to 

 a diflereut conclusion. One fact was that tho 

 meteors occurred in showers on certain 

 days. Take, for instance, the Nov. 13 shower. 

 "What could it mean 1 Why should a shower of meteors 

 take place on Nov. 13? There is no reason \vliy 

 meteors should show brlglitly ou tho 13tu of November 

 or any special day, so far as tho earth was concerned. 

 But, on Nov. 13, the earth is passing a particular p.irt of 

 its course. In November tho oarth, revolving around 

 the sun. when she reaches that part of her course 

 is cotluted by certain missiles which'' utriko 

 her atmosphere from without, and b.^oomo illuminated 

 in pasting through it. Tho inference is this. If a trav- 

 eler in passing along a certain r;ia;l found himself in a 

 certain place alwa>s saluieri with a shower of stones, ho 

 would conclude that some mischievous persons infested 

 that part of the road and amused themselves at 

 his expense. By tho wa> , this illu.-jtr.il l:>n which I m ida 

 In a forn.er lecture, was Hii-.iiig'h- nr.-i i;r;jroto 1 in a 

 morning pape?. I Mvke or i tin a:-lioolb M s throwing 

 stones at a travel -r; It w is d.-soiTicd us an 

 occu: lenri' happen! i _; i i K ul mil. a:i 1 to my horror I 

 found It in oue of the morning papers that it was cua. 



