68 BIOLOGICAL LECTURES. 



be resolved. The spectroscope, an instrument for determining 

 whether matter is solid or gaseous, when turned towards the 

 sky showed that there were vast numbers of gaseous masses 

 there and in many degrees of condensation. This discovery 

 was held to corroborate the idea of Kant and Laplace, so that 

 to-day there is no astronomer who does not hold the view that 

 the Solar system as we see it to-day is a growth, that it was 

 not made as it is, and that gravity with the simple laws of 

 motion are sufficient in themselves to organize the Solar 

 system as we find it, and an explanation of it is an exposition 

 of how these factors brought it about. 



The distribution of land and water, mountains, valleys, rocks 

 and their contents in like manner were held to be explained by 

 the statement that they were thus created substantially as we 

 find them. When it was noted that animal and vegetable 

 remains were to be found in abundance in many rocks, very 

 little thought was needed to induce the question : If these 

 rocks have been in place from the beginning, how came they 

 to be filled with evidences of marine life such as fossils attest } 

 Did the ocean once cover the mountain tops } Once the 

 attempt was made to explain their presence by reference to 

 Noah's flood which was held to have covered mountain tops, 

 but the fossils were to be found through great rock formations 

 and through rock depths of miles. It was noticed presently 

 that the lower formations had simpler forms and the lowest 

 rocks none at all. There was but one meaning to all this, 

 namely, the surface of the earth had been depressed and 

 elevated above their present level, that the ocean must have 

 once covered what is now a mountain chain. It was also noted 

 that slow changes in elevation are now going on in many places. 

 The coast of France is sinking, the coast of Norway rising. 

 The temple of Jupiter Serapis has twice been submerged in 

 the Mediterranean Sea and is now out of water. The Missis- 

 sippi River is building shores in the Gulf of Mexico at the rate 

 of a mile or two a year with the detritus brought from the 

 central valleys of the United States, and Niagara Falls is 

 retreating at the rate of a foot or two a year. Such phenomena 

 imply unstable land and water surfaces. The physical features 



