80 Tribune Extra* Pamphlet Scries. 



I was making comparison between Mr. Rutherfurd and light, became visible. 



Dr. Draper. 



There you have a picture of the full moon, and you 

 will notice how exceedingly dark these ridges are on 

 the bright upner region o. J the moon, and that wonder- 

 ful region which is called Tycho. and that wonderfully 

 bright region where crater overlaps crater, even as it is 

 there shown by the photograph aud rtdre remarkably 

 by a telescope of great power. Dr. Schmidt of Athens 

 has been counting the number of these craters, and 

 that number has pone on growing greater, until 

 at last a map of BO many has been made 

 that they cannot be distinguished one from another. 

 This work of Dr. Schmidt's was the noblest work of that 

 kind tliat exists, und it is very unfortunate that we can- 

 not get money enough in Europe to publish it, and 

 make him some remuneration for the work of so 

 many years. We will now have a map of the gibbous 

 moon, piasing on to the third quarter. This picture is 

 by Mr. Ruthenurd. Around the right of the moon we be- 

 gin to see a region about which a very important discus- 

 Bion has lately taken place. Low down on the right is a 

 ainall dark round spot, on this curved bright streak. lu 

 the middle of that is this dark round spot, called the 

 Floor of Plato. It looks very dark indued, especially in 

 the case of the gi'ibous moon. In the next picture you 

 will see how it becomes apparently lighter. When this 

 Is looked at closely, and certainly when looked at 

 through a telescope, it is found that it looks lighter at 

 the time of the quarters than at the time 

 of the full moon when brightly illuminated. 

 Now, it has been suggested that on that spot 

 eome process of vegetation is taking place. In that 

 case we should have a very striking fact of some 

 change taking place there. Unfortunately for that, it 

 happens that there is also a strong argument against the 

 theory that there has been any real change there. Of 

 course when you view the spot at the time of the quar 

 tcrs you have shadows thrown ; and m contrast with 

 those shadows, the floor of that spot naturally looks 

 lighter. Whereas in the case of the full moon, all around 

 it there is a brightly illuminated region. The mountains 

 have a great illuminating power, and therefore by con- 

 trast the spot looks dark. I have made the calculations 

 im self, anil found that that is absolutely the case ; in- 

 Ftradof growing dark with the full moon. It grows 

 lighter. It i.s a in. -re subjective effect, and wo have not 

 the evidence we booed for, evidence of change. Thera 

 lean illustration of that fact in the appearance of the 

 satellites of Jupiter in their transit across the face of 

 that pi. i not. Tiiey look black by contrast, but start into 

 brightness as noon as they move off the disk of the 

 planet. 



THE LUNAR MOUNTAIN'S. 



We will have tin* other picture, which Do La Ruo said 

 was better than any lie ever took himself. Wo have here 

 the moon in (Me tl.ini quarter. Ilere Is the lower region, 

 the Flour of Plato, here the lunar Apennines, hero the cra- 

 terof Copernicus, and here the lunar crater Aristarchus, 

 the very region where Sir John Herschol noticed a 

 bright ppot which ho took for an eruption. The fact was 

 that that very bright spot, by reflection of the earth's 



That -was the truth of It. We 

 will now have a picture of the very same thin?, 

 only mure distinctly shown; the details are somewhat 

 more distinctly shown. The Apennines can ba very 

 plainly recognized, passing in a curved streak upward. 

 H< re is Copernicus, here Kepler, and here Arist.irchus. 

 From these three centers there is a L-adiation, and it 

 appears clearly to observers that the strata wern up- 

 heaved at different times; the later ones seem to breair 

 through the earlier ones. It is hoped that by that char- 

 acteristic we c:in learn something of the chronological 

 order in which the changes of the moon's surface toofc 

 place. 



This picture has been enlarged by Mr. Rutherford. 

 Here is Copernicus and here you see the Apennines on 

 the lower lightened side. The moon you see is covered 

 all over with these irregular! ties. We know how voleauio 

 eruptions are brought about. First there is a gradual 

 contraction of the skin, the outer crust of tho 

 earth ; a mechanical efL-ct is produced, gases 

 are generated, and these gaar-s escape out 

 of the mouth of the volcano. If any sueh processes 

 happened upon the moon they must have been much 

 more violent. But then one would have thought than 

 any one of these lunar craters, tho largest bsing two or 

 three or four miles across, would bavo been large 

 enough to let all the gas in the whole 

 moon escape. Now, what was the necessity of 

 so manyl It was suggested by Dr. Ho,>k that 

 in a formi-r state of existence, there was a bubbling, and 

 as the bubbles broke these circular openings were 

 formed. We will have another picture brought on, still 

 further illustrating this. Here you will see the Floor of 

 Plato again, and the Apennines also, seen running 

 across toward the left of the picture. This crater is the 

 crater Aristarehus. 



We will now have that carried away, anil have an- 

 other series of pictures of a different kind. We will 

 have two pictures of the Floor of Plato. Yon will notice 

 that the shadows there are thrown on the Floor, in tho 

 picture on the right. In tho picture on the left, where 

 it is morning, you will notice how that long bank differs 

 from the appearance as presented on the right. You 

 recognize how far the appearance of the moon may 

 change, from a mere change in the illumination, and 

 how difficult it is to say that changes are going on, from 

 noticing the apparent changes. Here la an illustration. 

 It appeared that a certain crater had vanished, 

 as though a sort of cloudy matter had been 

 thrown out. When the supposed volcanic erup- 

 tion ceased, tho hills apparently had b.'OO 

 made more sloping, and the crater could not be so well 

 seen. But unfortunately for this supposed evidence of 

 change, tho crater has again appeared as before. Our 

 moon changes and shifts, not merely with regard to the 

 sun, but to the earth, and, by a calculation of mine, I 

 find that 1,300 years must elapse before you could see 

 any part of it again in the- same view exactly. 



You have now a picture of tho lunar crater Coperni- 

 cus. This picture is very difF-ront from that taken by 

 other observers. It is quite manifest that the skill of tha 

 artist has worked out tho picture iu a c^rniu w.iy 



