Botany and Zoology. 191 



methods appear to have been well selected and carefully carried 

 out. The results show that carbon dioxide and hydrogen are in 

 general the gases most largely evolved, while minute amounts of 

 carbon monoxide, hydrogen sulphide, methane and nitrogen are 

 apt to accompany them. The author recognizes, of course, that 

 a considerable, or even the larger, part of these gases were not 

 contained in the rocks as such but were evolved from carbonates, 

 sulphides and hydrates, and he discusses their possible origin from 

 these substances and from others not known to be present in 

 rocks, such as carbides and nitrides, but which might conceiv- 

 ably be present in the igneous ones. Rocks, however, are such com- 

 plicated bodies and the possible reactions and interactions which 

 may take place at high temperatures so many and so involved 

 when a large number of factors .are concerned, as brought about 

 by the possible presence of sulphides, metallic oxides of a lower 

 state of oxidation, carbon and even metallic particles such as 

 copper and iron, that it appears possible that all of these gases 

 except the nitrogen may have been produced from original solids, 

 sulphides, carbonates and hydrates. While some of the gases 

 such as CO Q and water vapor are undoubtedly contained in rocks 

 as such, it thus becomes a matter of doubt as to how much of 

 the gases evolved are to be considered original and how much 

 ascribed to secondary alteration of the original minerals. In this 

 connection the reviewer regrets that the work was not accom- 

 panied by a microscopical examination in thin section of the 

 actual specimens studied, since this would have thrown much 

 light upon the presence or absence of such secondary products. 



In conclusion the author discusses the bearing of the results 

 obtained upon general problems of geology and with reference 

 to the early condition and origin of the earth. While no essen- 

 tially new or startling facts have been brought to light by this 

 undertaking, it is none the less a very useful piece of work of 

 a laborious nature which has been carefully carried out and 

 which will prove of service in the future in aiding to solve 

 problems of chemical geology. Many investigations of just this 

 character are needed before speculation upon the early history 

 and character of the earth's crust can rest upon secure founda- 

 tions, l. v. P. 



III. Botany and Zoology. 



1. The Forest Flora of New South Wales; by J. H. 

 Maiden, Government Botanist, and Director of the Botanic 

 Garden, Sydney. — This useful treatise has now begun its fourth 

 volume. The training of the author for this important contribu- 

 tion to science has been of a peculiar character. After having 

 familiarized himself with the most approved Museum methods in 

 England, he took charge of the great economic Museum in 

 Sydney, where, under many discouragements, he built up a vast 



