REVIEWS. 
179 
We have never seen any elementary book on mineralogy — ever especially a dif- 
ficult subject to siniplily — in which so much really scientific bounding was so 
naturally and intelligibly put. The reader is first introduced to the forms of 
minerals, then of crystals ; then to the characters of hardness, specific giavity, 
electrical ancl chemical q^ualitics, &c. ; thence he is led to special mineralogy, taking 
first in order the precious stones ; then follow in due succession, the augitic 
minerals, the felspatliic, micaceous, zeolitic, and the calcareous. Compotmds of 
baryta, of strontia ; salts of potash, of soda, of magnesia, of ammonia ; combus- 
tible matters ; the metals and their ores. 
The following passages describing the use of the blow-pipe in mineral analysis, 
will aftbrd an example to our readers of the unassuming, easy, and simple, and 
yet thoroughly scientific style in which the book is composed : — ■ 
" As the purposes to which minerals may be ajiplied, as well as the knowledge 
of individual species, stand in very close relation to then- chemical composition, it 
is important to acquire dexterity ui the analysis of minerals ; and for this pur^rose 
either the moist or dry method may be employed. The latter consists principally 
in the use of the blow-pipc, the former in the solution of bodies in water, acids, 
&c., and the a])plication of certain re-agents by which precipitates of particular 
colours and conditions are thrown down. In both cases the object is either to 
obtain decomposition, or new combinations, which may once more be analysed. 
" In using the blow-irlpe, small fragments of the mineral may be held either on 
charcoal or in platinum forceps ; so that, first, the fusibility, and then the 
escaping vai)onr or deposit left on the charcoal, as well as the residue, is examined, 
either by reducing it in the inner fiame, or by forming from it, along with borax, 
soda, or salt of phosphorus, a pearl-like di'op, which is also to be considered with 
reference to its colour and appearance. It is to be kept in mind, in using the 
blow-pipe, that the point of the flame has an oxidiziny power, and the inner blue 
cone has a reducing influence, that is, it has the power of deoxidizing ; also that 
metals easily fused or reduced should not be held in> the platinum forceps. Many 
bodies, such as chalk, become exceedingly brilliant when heated, others coloiu- the 
flame at once, or after being held in it for some time. Thus, for example, all 
calcareous minerals colour it vermilion-red, strontium gives a brilhant purple-red, 
lithium a pale purplish-red, potassium a violet, sodium a piu'e intense yellow, 
baryta a green, boracic acid a pale green, acetate of copper a green, chloride of 
copper a blue, and the presence of chlorine may be easily distinguished in this way 
by tne addition of some oxide of copper : while, on the other hand, the presence of 
copper, be it of ever so small amount, may be easily recognized by the bright blue 
flame on moistening the test with a drop of hydiocliloric acid. The colour which 
certain metallic oxides impart to a bead or pearl of borax, which has been obtained 
bv burning on charcoal, when heated on a platinum wire, is likewise important 
Thus, the oxide of cobalt colours it blue, the oxide of copper imparts a green 
colour, and, if a gi-anule of tin is added, it becomes red ; peroxide of iron 
makes it yellow when hot, and olive-green when cold ; protoxide of iron gives a 
grass-green, oxide of chicmium an emerald-green, oxide of manganese an ame- 
thyst-red, oxides of manganese and u'on together give a blood-red or gamet-colonr, 
and so on ; while the oxides of zinc, lead, and bismuth do not change the colour of 
the bead. Further details will be found in the description of the individual 
minerals. The analysis by water is best performed in a closed glass-tube, or in a 
small retort over a spii-it-lamp, by which means small drops are deposited on the 
colder part of the tube. This experiment serves at the same time to distinguish 
the water from the carbonic acid, both of them producing small beads in the 
borax pearl. 
" The presence of carbonic acid is best recognized int he moist way, by solution 
in hydrocnloric and nitric acids until eff'ervescence takes place. Sulphur and sul- 
phuric acid may be detected by using fijiely-powdered specimens along with soda 
m the inner flame, by the aid of which a sulpnuret of soda is produced, and this, 
when moistened by a drop of water, and brought into contact with a silver coin, 
leaves a brown stam, and gives oft' an odour of rotten eggs (sulphur'etted 
hydrogen). 
" The presence of siliceous earths is best ascertained by melting the powdered 
mineral along with borax or soda, while to the clear pearl which is formed there 
