REMARKS ON MR DARWIN'S THEORY. 



183 



oxygen, less carbonic acid — after a plant has grown in it than before. 

 True, they give ont carbonic acid at night, but not so much as they 

 take in. All the plant (except water) is so much gained from this 

 carbonic acid. Hence, the air is purified by plants. 



Now coal being of vegetable origin, it is calculated that for every 

 pound of coal, all this carbon, and at least two pounds of water have 

 disappeared from the atmosphere. And if we consider the millions 

 upon millions of tons, fixed in solid black masses in the crust of the 

 earth, we must see that we are living in an atmosphere far purer, and 

 more fit for the respiration of the higher animals, than it could have 

 been without the aid of coal. 



It may have been, as the sagacious De la Beche observed, that 

 this enormous supply of carbonic acid was due to the ejections from 

 many volcanic months, which we know breathed forth their fiery 

 exhalations in coal times. It is also true, as Sir C. Lyell has said, 

 that these gases so readily mix with the atmosphere, that little appre- 

 ciable difference would be made by any quantity of volcanic action. 

 But look at the subject in any light we may, there was the carbonic 

 acid in the air, and there it now is, for our benefit, in the earth. 



This rank vegetable produce, then, of quick growth and soft tissue 

 — constantly wet, fermenting as soon as covered up — its heat kept in 

 by a blanket of wet sand or clay, with pressure for ages, gives us all 

 the conditions necessary for the production of lignite, brown coal, 

 jet, and pit- coal ; and when volcanic heat had driven away its gaseous 

 parts, and left the carbon pure — even anthracite. 



As this month's communication has extended to an unreasonable 

 length, I will not now enter into the question of the different qualities 

 of coal, or its uses, but defer what little I have to say on those 

 subjects till next month. 



SOME REMARKS ON MR. DARWIN'S THEORY. 



By Frederick Wollaston Hutton, F.G.S. 



(Continued from page 136). 



But there are other causes that have tended to modify animals ; 

 such as habit, use or disuse of any particular organ, food, climate, &c, 

 and these together with the fact that a variation which appears in the 

 parent, at any period of its existence, tends to re-appear in the off- 

 spring at the same period, will enable us to account for the metamor- 

 phoses of insects, the differences of colour in the young and the 

 adult, the horns of sheep and cattle, &c. If to these we add that of 

 " sexual selection,"* we can see why sexes differ in organs and pro- 



* Sexual Selection may be defined as the preference shown by an individual of 

 one sex for an individual of the other from superior beauty of colour, shape, voice, &c. 



