(Scientific Lectubes. 125 



came out under our briglitest telescopes. Still tliere -were certain, 

 masses of light which Herschel could not resolve, but which other 

 observers discovered to be made up of suns or of stars, and hence the 

 nebulous hj-^^othesis fell into doubt. It was said that still more 

 powerful instruments will enable us to show that these nebulous 

 masses are made up of stars. There came in a very unexpected aid 

 in the spectroscope. With this instrument, in the examination of 

 light in the first place from terrestrial sources, it has been found that 

 you can discriminate between the light that comes from a solid body 

 and the light which comes from a vaporous, gaseous body ; that you 

 can pierce distance and resolve problems in the investigation of which 

 the most powerful telescope was impotent. We have now discovered 

 that in the sun and in the fixed stars we have present the very same 

 elements as are those of our earth, and we may thence conclude that 

 the same chemical laws which hold good in our planet hold good in 

 all bodies of the solar system. We miglit, therefore, conclude not 

 only the unity of our system, but the unity of all systems, and all 

 worlds, and we are enabled by comparison between these and our 

 own planet to show that all these nebula, suns and planets are worlda 

 in so niau}' successive stages of development, of wliich our own makes 

 perliaps one of the latest and most completely accomplished stages. 

 HaviTig this great luminous or nebulous mass, the natural incpiiry 

 W'as wliat were the laws which regulated its condensation, how should 

 it ever become reduced to the condition of a solid globe ? By the 

 simple process of cooling. The sun, the great center of our system, 

 was a cooling body. It Avas a body, constantly giving off light and 

 heat, constantly losing light and heat, and therefore slowly but surely 

 undergoing a cooling process. When we investigate the laws of 

 cooling bodies, and still more when we investigate the chemical 

 changes in bodies at a greatly increased temperature, we learned 

 anotlier curious lesson, which was, that at intense temperatures, such 

 heat as must exist in the sun and in the nebula, almost all bodies are 

 in a state of chemical indifference. He did not know that he could 

 make himself plainly understood, but he would refer to the composi- 

 tion of water. This was known to be produced by the combination 

 of oxygen and hydrogen gases. These, combined with an evolution 

 of heat to produce water, out if you exposed water to a very much 

 higher heat than that by which it was formed, it would break up 

 again into oxygen and hydrogen. So we find that almost all compound 

 bodies known in nature, when intensely heated, are decomposed. It 



