Cleaveland on Mineralogy and Geology. 399 
Class 2. Earthy Compounds, or Stones.—Composed chiefly 
of earths combined with each other; they frequently contain 
some metallic oxide, and sometimes an alkali or acid. This 
class contains 90 species, arranged according to their chemical 
composition, which is denoted on the outside of a bracket, on 
the left hand of the respective groups. The first consists of 
silica nearly pure, guartz, &c. ‘The second, of alumina nearly 
pure, sapphire, &c. Then succeed the compounds of alumina 
with water, magnesia, silica, &c., in which that earth is the 
chief ingredient, and proceeding from the more simple to the 
more complex combinations. After these come the compounds 
of yttria, and of zirconia, with silica, &c.; and lastly, those 
(by far the most numerous) in which silica is the principal 
element, in combination with one or more of the other earths. 
This arrangement obviously bears a close analogy with that 
adopted by Mr. Wm. Phillips. At the end of this class are 
placed 22 species not yet analyzed. 
The third class comprehends the combustible substances, 
and we were somewhat staggered at seeing hydrogen gas stand 
at their head. In the Natural History Method we are not sur- 
prised to see it, but here we are both surprised and sorry. After 
hydrogen, come sulphur and the other combustibles, including 
diamond, and 
The fourth class is devoted to ores, beginning with gold, 
platina, &c., and ending with selenium and cadmium. 
The descriptions of the species in the body of the work are 
ample, without being diffuse, and always clear. The general 
description is usually succeeded by that of the chemical cha- 
racters, distinctive characters, and geological situation and lo- 
calities. The latter head is particularly useful, as respects the 
mineralogy of the United States of America. We regret that 
our limits forbid us to quote any instances of Mr. Cleaveland’s 
style, in this important part of his book ; we hope its universal 
distribution will render the omission of little consequence. 
The same want of space compels us also to notice, much 
more cursorily than we could wish to do, the remaining part, 
the Introduction to the Study of Geology. After some general 
remarks, and the explanation of the terms primitive and second- 
ary, as applied to rocks, a description of their relative ages and 
positions, &c., the author sums up the whole in the following 
general principles, which he considers as “ satisfactorily esta- 
blished :” 
1. The minerals which compose the external crust of the globe, from the 
summit of the highest mountain to the lowest point hitherto explored, must 
at some former period have been in a fluid state, and the solyent must un- 
questionably have been caloric or water, 
2. There appears to be sufficient reason for believing that by far the 
greater number of minerals have been kepusited froma state of solution or 
suspension in water ; and of course, that tke sea, in a more ov less tranquil 
