212 Bibliography. 



mental inquiry into matters where certainly experiment and inquiry are 

 yet much needed, and is therefore at least entitled to an unprejudiced 

 and candid hearing. The volume is mainly occupied with a detailed 

 account of a series of numerous experiments, made by the author, on 

 the chemical changes that take place during the growth and decay of 

 plants. From these the deductions are simply and directly drawn ; so 

 that whatever credit is given to them will depend mainly on the ac- 

 curacy and value of the methods employed in the experiments, which 

 are so fully detailed that they may be readily repeated and tested. A 

 few of the author's most important deductions are subjoined, 



1. Plants impart to the atmosphere more carbonic acid than they re- 

 move from it. 



2. In the process of vegetation the carbon, which goes to the growth 

 of the plant together with that given off in the form of carbonic acid, is 

 very considerably greater than can be accounted for by its disappear- 

 ance from all the sources by which the plant is supplied. Carbon is 

 therefore a product of vegetation. 



3. The quantity of carbon made by plants is affected by a variety of 

 circumstances, such as the nature and quantity of the soil, temperature, 

 miasm, saline and earthy bodies, carbonaceous matter in the soil, quanti- 

 ty of water supplied, and by the presence of carbonic acid in the atmos- 

 phere. 



4. During the putrefactive fermentation a portion of carbon is decom- 

 posed ; for it is not to be found in the carbonic acid disengaged, or in 

 any other of the products, while in its place water and miasm are ob- 

 tained. 



The author adds at the close of his book, " My observations, during 

 the whole course of my experiments, have led me to the conclusion that 

 of the elements carbon, hydrogen, oxygen, nitrogen, sodium, potassium, 

 calcium, &c., which constitute the organic and inorganic elements of 

 plants, hydrogen is the only ultimate element, the rest being compound 

 bodies ; and to question the compound nature of hydrogen." What- 

 ever may be thought of this, the experiments contained in this vol- 

 ume must be welcomed as a valuable contribution to our stock of 

 knowledge in this obscure and intricate department of science. 



G. H. 



