PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 601 



forth by the last speaker. Professor Stevens, in giving his own 

 views, proposed to occupy the attention of the audience liut a 

 short time. Leibnitz, in his day, brought forth the theory that 

 in one age the world was a molten mass, and being in this liquid 

 condition it assumed the spheroidal shape. In process of time the 

 crust thickened by cooling of the sphere, and so there was a space 

 or vacuum underneath it, and the crust fell in toward the centre 

 of the earth. (The speaker illustrated his remarks by diagrams 

 on the blackboard.) That hypothesis has had many able defend- 

 ers, and no better one than Prof Dana, of New Haven. He would 

 •not go further, but state that he denied that the earth was ever 

 molten, as all the facts are better explained by some better 

 hypothesis. The chemical geologists are rapidly giving way to 

 this new theory. He did not say that it might not have been so* 

 he only denied, from what we know, that it was so. In Germany, 

 after Leibneitz's time, there arose the Wermerian theory that all 

 the rocks were formed by the agency of water. Then ao-ain the 

 Huttonian theory that heat w^as the grand agent. Now he denied 

 from anj^ positive knowledge that we have, that any of these the- 

 ories are correct. But how came continents into existence, are 

 questions that wnll naturally arise. At the last and the present 

 meeting of the Polytechnic, we had a very able theory that it was 

 currents that produced continents. This he also denied, for we 

 have no reason Avhatever to suppose that at any age of the globe 

 there was an ocean of uniform depth, so he said there were no 

 geological premises on which this last theory can be based. 



Now, as to currents. Currents cannot create; they simply 

 receive into their bosom, and transport whatever they receive; and 

 when currents cease, then a deposit takes place. If the current is 

 rapid and of great volume, it bears along with it what is heavier, 

 and when the current ceases, as at high and low tide, then a 

 deposit takes place; but these tidal dejiosits have been altered 

 they have been variously altered, by earthquakes and other agents 

 in precisely the same way that Prof. Beck's experiments have 

 shown, and have made this entire continent just as we see it 

 to-day. 



We know that at one period of the earth's history, the point of 

 land at St. Anthony's Nose was the j)oint d''ap2yui from which this 

 continent in this latitude and longiuide was built, and another at 

 the Black Hills of Nebraska, and the great valley between, has 

 been filled up, and this has been done by tidal deposits; after this 



