Tribune Extras Pamphlet Sena. 



but yet., perhaps, Is better suited In other respects for 

 observing nebulae. You will have next another picture 

 brought ou showing a, different appearance from that 

 jiow outhe screen. You will have the great spiral nebula, 

 tea seen from tbe Rosse Observatory, and not indicating 

 all the enormous extension of that nebula. You s:>o 

 there a process as though some great quantity of nebu- 

 lous matter bad floated in with a spiral motion, travel- 

 lug through a resisting medium, and in appronohing the 

 center it traveled on a spiral course. Out: argument in 

 reference to that is that it was mutter of siiu.ll 

 density traveling in matter somewhat less dense. Hero 

 is another different picture of the great Orion nebula, 

 which has been compared to the mouth of some 

 gigantic sea monster oat picture was obtained by Sir 

 John Herschel with one of his father's telescopes that 

 toe used at the Cape of Good Hope, and to show the ef- 

 fect produced by different telescopes on the appearance 

 of nebula, we will have that picture removed and place 

 another picture of the same nebula on the screen, the 

 picture obtained by Bond when using the great refractor 

 of the Cambridge University. 



And let me here mention the superiority of the refrac- 

 tor at Cambridge to the Rosse telescope, and let rne 

 allude, also, to the possibilities of great future dis- 

 coveries by means of a telescope to be five feet in 

 aperture, which it is said your optician, Alvan Cl^rk, 

 proposes to make, at a cost, I believe, of $1,003,000. That 

 amount will be wanted. It seems a considerable sum. 

 But if any one can do it it is Clark, for he is unrivaled 

 as an optician. Cooke of England was the only optician 

 comparable with him, but Mr. Cooke is dead. I have 

 never had an opportunity of making any com- 

 parison between the great telescope of Cooke, 25 

 inches ia diameter, which is used in an inferior 

 atmosphere, and was completed in the hands of his suc- 

 ces-or, au<l those of Clark. The telescope at Washington 

 Is 26 inches in aperture. But now that Cooke is away, 

 Clark is the greatest of living opticians, and if a tel- 

 escope is to be made of enormous aperture, to be used 

 in California, it is to be boped ho may be spared 

 to make it. Another picture is now brought on the 

 screen Orion's nebula. You see these irregular starry 

 clomts. Thf.v give a spectrum altogether different in 

 character from the spectrum given by star-clouds con- 

 sisting of separate stars. These last give a rainbow- 

 tinted spectrum, showing they consist of suns resem- 

 bling our own in structure. This nebula now on tho 

 screen Is called the true lover's knot. Nebulro such as 

 that give spectra indicative of the gasinty of 

 the source of liglit. They spread through all thcso 

 wonderful depths of space. Remember their distauca 

 from us, and the length of the earth's orbit by which it 

 Is nieaiured. We have tho diameter of that orbit as 

 183,000,000 miles. Compared with tho stars' distance, the 

 whole orbit of our earth sinks into insignificance. And 

 remember tiiat the least of thcso stars its mere disk- 

 baa enormous heating power ; then remember how great 

 the distance from star to star of those shown in tins 

 view, and then consider that tills nebulous matter ia 

 spread between these stars and continues from one star 

 to another, and then yoa have an idea of tho wonderful 



extension of that matter. Neptune hag a diameter 30 

 times greater than the earth, and a globe such as that, 

 if placed on that picture, would be less significant than 

 the little star to which I point; and when 

 you cotue to the nebular hypothesis, when yoa 

 come to consider that fully, you will find that of the 

 nebulous mass that exists in that space there is abund- 

 antly sulh'cient material out of which solar fcystoma 

 could be formed. Wo will now pass to another system, 

 showing a great nebula, which is remarkable in thia 

 way, that it has varied in brightness. There S'-ems to bj 

 an association between the nebula and the star to 

 whoso influence It seems exposed. Herschel noticed a 

 star in Argus which at one time appeared to be a 

 star of the second magnitude ; fifty years later 

 it had sunk to the fourth magnitude ; when Herschel 

 noticed it, it was of the second magnitude, and it rose 

 to the first while he was at the Cape of Good Hope, and 

 when he came home he heard tu^t it had risen until ita 

 brightness exceeded every star m the heavens with tho 

 exception of Sirius. At this moment that star can only 

 be seen on the darkest and clearest night. It shows now 

 with luster less than the one-hundredth part of what it 

 had a quarter of a century ago, suggesting this idea, that; 

 many of the planets are not fit to be abodes of life* 

 80 there are many stars of which this is a typo, stars 

 which are unfit to be the centers of circling 

 worlds, simply because their light is so variable. 

 If that star were the center of a system, a 

 quarter of a century ago it was a great deal too bright, 

 if on the other hand a quarter of a century ago it gave 

 out the right kind of light, it is now too faint. We will 

 pass from this object to another which illustrates tho 

 connection between tho neliuhe and stars. Fora long 

 time the theory was that this iie'mlous matter was far 

 away out in space from tho stars, but when you look at 

 the group such as you now see, you will recongnize tho 

 fact that there is a connection between the nebulous 

 mass and stars. Wo will have bore a portion of tha 

 great Orion nebula, which is found to have branches 

 extending from the central part of tho nebula to tlio 

 star Iota and UD ward to tbe star Epsilon, and you will 

 observe nebulous streaks stretching from star to scar. 

 You may view them as tho fingers of a mighty baud, 

 showing beyond all possibility of question there is a 

 real connection between tho nebulous matter and tho 

 star seen in the same view. 



Tho great astronomer, Kepler, discovered tho threo 

 fundamental laws of tho solar system. Now, he im- 

 agined that tho center of tbe universe was the solar 

 system. He considered that the light and beat of tho 

 pun spread out and was caught up by a shell, inclosing tho 

 ptars, and there was none of the waste of which 1 spoko 

 in uiy first lecture, and ho made a scries of calculations 

 which have not the least trustworthiness In them, and 

 camo to tho conclusion that tho shell of tho uuivurso 

 is 70 miles in thickness. 



I now pass to Wright's theory, which is commonly 

 ascribed to Sir William Herschel, that our starry system 

 Is one of several starry systems. As you know, Hcr- 

 chel ganged tho heavens, and, because bo found th- 

 itara were great In number in tho direction of the 



