;>6 DR. FOWNES ON THE EXISTENCE OF PHOSPHORIC ACID IN ROCKS. 
These were all the substances tried ; they were taken, as is at once seen, indis- 
criminately from igneous formations of many localities and many ages, and they all, 
with one doubtful exception, in which practical difficulties interfered with the inquiry, 
yielded phosphoric acid. It is highly probable, therefore, that this substance is a 
very usual, although small, component of volcanic rocks. 
It is not unlikely that the remarkable fertility possessed by soils derived, from the 
decomposition of some varieties of lava may be, in part, at least , due to the presence 
of this phosphate in the original rock, although much must of course be ascribed to 
the alkali, especially potash, which these substances contain, and which is gradually 
brought by the continued process of disintegration into a soluble state. There can 
be little doubt that the matter erupted from time to time from the interior of the 
earth, in a state of fusion, is thus destined to renew the surface from which the 
more valuable and more soluble 'components have gradually been removed by the 
action of water and other causes constantly in operation. If it should hereafter be 
found on a more extended investigation that phosphoric acid, although present in all 
igneous rocks, is most abundant in those of modern date, the fact will thus receive 
an explanation, the more ancient lavas having been most changed by the slowly-act- 
ing and almost imperceptible causes in question. One might be tempted to consider 
lava as a kind of fundamental material, from the subsequent alteration of which all 
others are derived, and expect it to contain, here and there at least, traces of all the 
elementary bodies known, even those most rare. In the present case, it cannot be 
altogether devoid of interest to trace to its first source the enormous quantities of 
phosphoric acid, for the most part locked up in a temporarily insoluble condition in 
the vegetable and animal kingdoms, and in the various strata of calcareous and sedi- 
mentary deposits, in the formation of which organized beings have played so promi- 
nent and so important a part. 
6 Coventry Street , 
April 1 7, 1844. 
