REPORT ON MINERALOGY. 
343 
by his ingenious methods, whether the acoustical elasticity was 
also governed by similar differences. We ought not to overlook, 
in this comparison, the circumstance that the term <£ elasticity ’ 
is here applied to two different classes of phenomena, referable 
to different principles ;—the acoustical phenomena depending 
on the elasticity of the parts of the solid , the optical on that of 
the optical aether. Savart found that some of the acoustical 
differences of elasticity correspond to the optical relations, 
but also that there are other acoustical differences following a 
different law of symmetry. In a common crystal of quartz, a 
transverse plate (perpendicular to the axis,) has the elasticity of 
all its diametral lines equal; but though all the plates cut paral¬ 
lel to the axis have the same optical properties, their acoustical 
properties have a relation to the edges of the prism ; such, how¬ 
ever, that any three plates at angles of 120° have equal acousti¬ 
cal elasticity; he found also, that by the acoustical properties he 
could determine the cleavage planes of quartz; he made like 
observations on calc spar, and some of equal interest on metals. 
These, it appears from his researches, have a structure neither 
regularly crystallized nor altogether uncrystalline; their pro¬ 
perties are different in different directions, and they give, by 
their vibrations, corresponding differences of note, amounting to 
a tone; yet, as it is found that parts taken from the whole have 
not properties identical with those of the whole, the composition 
is not a repetition of that of small parts, as in regularly crystal¬ 
lized bodies. It is extremely interesting to see the sciences of 
colours and of sound thus uniting to give us that information 
indirectly concerning the internal structure of minerals, which 
we have so long attempted in vain to obtain directly. 
4. Chemical Mineralogy . 
In entering upon the Chemistry of Mineralogy, we come to 
that part of the subject in which undoubtedly the greatest 
labour has been employed and the least progress made. That 
this is not too unfavourable a judgement will be clear, I con¬ 
ceive, w r hen it is considered how numerous and operose have 
been the analyses of mineral substances executed by all the best 
chemists during the last century, and yet how scanty and un¬ 
connected our knowledge on this subject still is. Not only are 
there no general and generally recognised chemical laws, capable 
of being predicated concerning extensive classes of mineral 
bodies, but the constitution of any particular mineral species, 
with the exception of a few, is a matter of doubt and dispute ; 
and we shall hardly be contradicted when we say that there are 
very many cases in which, if we were to state to the chemist 
