338 KANSAS CITY REVIEW OF SCIENCE. 



thought that they favored the photographic system. He hoped that the astrono- 

 mers in America would do all their duty in the matter in the interests of posterity. 



EVOLUTION OF THE EARTH. 



Rev. Samuel Haughlon, D. D., Fellow of Trinity College, Dublin, read a 

 paper Monday morning in Section A on "New Views of Mr. George H. Dar- 

 win's Theory of the Evolution of the Earth, — Moon System, considered as to its 

 Bearing on the Question of the Duration of Geological Time." He said: It has 

 been tacitly assumed, even so far back as the times of Newton and Clairvant, 

 that the earth and planets have passed through a liquid condition (owing to form- 

 er great heat) before assuming this sohd condition which some (at least) of them 

 nowpossess. 



Laplace, in his nebular hypothesis, also assumes the former existence of this 

 liquid condition, and it is openly assumed by all geologists who believe that the 

 earth consists of a soUd crust (more or less thick) reposing upon a fluid or viscous 

 nucleus. 



It has been asserted by Sir William Thompson, following out the views of 

 the late Mr. Hopkins, that the present condition of the earth taken as a whole, is 

 such that it must be regarded as being more rigid than glass or steel, probably 

 more rigid than any terrestrial substance under the surface conditions of pres- 

 sure. The following conditions show that it may be fairly douted whether the 

 earth or any planet ever existed in liquid conditions. 



1. The possibility of the equilibrium of the rings of Saturn, on the supposi- 

 tion that they are either solid or liquid has been more than doubted, and the 

 most prbable hypothesis respecting them is that they consist of swarms of discrete 

 meteoric stones. 



2. It is difficult to understand the low specific gravity of Jupiter and the 

 other outer planets, on the supposition that they are either solid or liquid, for we 

 know of no substance light enough to form them. The force of this argument 

 could not be felt before the revelations of the spectroscope, because at that 

 time there was no proof that the whole universe was composed of the same simple 

 substances, and those very limited in number. If the outer planets consist of dis- 

 crete meteoric stones, moving around a solid or liquid nucleus, the difficulty re- 

 specting their specific gravity would disappear. 



3. The recent researches connecting the November, the August and the 

 other periodic swarms of shooting stars with comets tend in the direction of show- 

 ing that comets in cooling break up into discrete solid particles, each no doubt 

 haying passed through the liquid condition , and that probably the solar nebula 

 cooled in like manner into separate fiery stars, which soon solidified by radiation 

 into the cold of space. 



4. Mr. Higgins' recent comparisons of the spectroscopic appearances of 

 comets and incandescent portions of meteoric stones, showing the presence in 



