174 
ON THE CONTENTS OF THOMSON’S WORK. 
her without any method, but that each 
mineral species which is met with on our 
globe, is formed of elements definitely com- 
bined ; and that a cabinet of minerals ought 
to constitute part of every chemical museum, 
as essentially, as soluble and other salts which 
were formerly considered as distinct from the 
mineral kingdom. This was easily proved, 
in reference to more simple minerals, whose 
elements were found to exist, combined in 
atomic proportions, both in artificial and 
natural salts. Thus, the atomic weights of 
8ul phuric acid and lime being determined when 
entering into the composition of what were at 
first ascertained to be atomic compounds it 
was but reasonable, on the occurrence of these 
bodies in a native state, to assign to their ulti- 
mate particles the same atomic weights. Ac- 
cordingly, sulphate of lime has been found 
abundantly in a native state, in two states, — 
first, as Cal. SI 2 Aq, and second, as Cal. 
SI. In both of these instances the atomic weights 
of the sulphuric acid and lime were precisely 
the same as in the more familiar salts, sul- 
phate of soda, muriate of lime, &c. Having 
ascertained that this held good in regard to 
one or more minerals, chemists were induced 
to extend their researches over the field of 
nature. They gradually discovered that some 
bodies possess actions which they would have 
long looked for in vain, if they had neglected 
this delightful and varied field of investigation. 
They found that a mineral termed Table 
Spar, afforded, by the analysis of eight dif- 
ferent specimens from different localities, 
always, the same quantities of silica and 
alumina. — about 5l parts of the former, 
and 45 of the leiterAnother mineral, Picros- 
mine, gave by analysis, 56 parts silica and 
36 magnesia. What, then, were the legiti- 
mate deductions to be drawnfrom these 
analyses? Was it not correct to say that 
the silica acted the part of acid to the lime 
and manganese, as did the sulphuric 
acid in the instances previously alluded to? 
Hence the formulae for table spar and picros- 
mine, it has been inferred, are Cal. S2 and 
MgS2. The discovery that silica acted as 
an acid, in simple combinations, was sufficient 
to entitle chemists to conclude that this im port- 
ant body continued to preserve its power of 
action in more intricate compounds, where 
several bases presented themselves, upon 
which it might exercise its agency. If in the 
case of the table spar, an atom of iron had 
been present, we should have had Cal. S 
X FS ; the formula would have been extended 
the composition would have been somewh at 
more intricate ; and, if we had a tiiird atom 
of silica, as in tersilicate of lime, we might 
have had a third base united with the third 
atom of acid And all this with as much 
propriety as there is in representing the com- 
position of the rrore familiar salt, alum, by 
KSI.4-3 Al.Sl. + 25 Aq. 
To those who have occupied themselves 
with the important study of the mineral king- 
dom, we know that these observations are 
quite superfluous ; but they may properly be 
urged in answer to such as term the analysis 
of stones (as they sneeringly designate the 
labours of the analyst) an abuse of the atomic 
theory ; and they are peculiarly applicable in- 
turning our attention to the new work on 
mineralogy and geology, whose title stands at 
the head of this article. The first volume 
consists of a description of 509 different species | 
ot minerals ; the greater proportion of which | 
have been subject to analysis, either by the i 
author himself, or under his superintendence ; 
and those, alone, can judge of the activity and 
enthusiasm with which, during the last ten 
years, these labours have been engaged in, who 
have been employed as fellow-workmen in the 
delightful, though ardous task. Before a pro- 
perly arranged system can be formed, theele- 
ments of that system must be examined. Not 
only have the elements been scrutinized in 
the present instance, but they have been 
reduced into order, and of such a nature, as, 
we conceive, infinitely surpasses any which 
has been previously proposed. By the 
systems hitherto propagated the most dis- 
similar bodies have been associated. The 
classification of minerals, as of salts, should 
be simple, not complicated The arrange- 
ment in the British Museum belongs to the 
latter class, and must be pionounced bad. 
The acids there distinguish the classes, and 
hence, the greatest confusion is produced ; 
for the salts of each base constitute as many 
classes as the base forms combinations with 
acids. Thus lead is found in combination 
with at least seventeen different acids. These 
different minerals will, therefore, according 
to this arrangement, be deposited in seven- 
teen different places. The base, however, 
of a salt, gives character, generally, to all 
the bodies into which that base enters as an 
element, the acid does not afford any such 
general character. If we class together the 
different sulphates, for example, we have 
bodies associated of all hues and dyes; but 
if we place the salts ot copper in juxtapo.si- 
tion, the merest tyro would instantly discover 
the propriety of such an arrangement. This 
is the plan which has been adopted in the 
present work. 
Such is a general view of the contents of 
the first volume. It commences with an 
introduction explanatory of the nomenclature 
of the external characters of minerals, and 
exhibiting a view of the system of crystal- 
lography adopted by Mohs, for the purpose 
of enabling the English reader to consult 
Haidinger’s admirable translation of Mohs’ 
works. The volume concludes with three 
tables, in the first of which are given the 
specific gravity, hardness, and form of the 
crystals of minerals, in the order of the chemi- 
cal arrangement. The second affords a list 
of minerals arranged according to the spe- 
cific gravity, beginning with Scheererite the 
lightest , and the third supplies^ a list of 
minerals in the orderof their hardness. Mine- 
ralogists will at once appreciate the utility 
of these tables. 
The first 345 pages of the second volume 
are devoted to an outline of geology, and 
a valuable and complete table of the fossils, 
plants, and animals found in the mineral 
kingdom. 
The first chapter, on the d'emperature of 
the earth, is full of most important matter. In 
