4 
The ultimate source of all our supplies of the valuable metals 
is the magma or molten rock of the primeval surface of the globe. 
No one has positively identified any mass of this magma in either 
still fluid or congealed form, but a study of the visible products of 
its alteration enables ns to arrive at a very fair estimate, though 
admittedly not a rigid one, of the quantities of those valuable 
constituents which were presumably more or less homogeneously 
distributed through the primeval magma. On the basis of the 
numerous rock analyses which have been made all over the world, 
and upon calculations of the relative quantities of the different 
rocks disclosed at and near the surface, estimates have been made 
from time to time of the average quantities of the various elements 
distributed through that comparatively thin crustal portion of 
the globe, the so-called “ lithosphere,” which is within reach of 
li\ dug organisms and man in particular. These estimates are 
rather startling at first sight, since they show that out of 83 known 
elements the majority of which has become indispensable to us, 
two, viz., oxygen and silicon, together monopolise 75 per cent, of 
the whole earth’s crust. Only six others are present to the extent 
of between one and ten per cent., viz., aluminium, iron, calcium, 
magnesium, sodium and potassium ; and three others, titanium, 
phosphorus and hydrogen are present to the extent exceeding one 
part- in one thousand. Of the remaining 7 2 elements, several like 
carbon absolutely essential to life, 11 are present in quantities 
less than one part in one thousand, whilst others equally essential 
to our present day machine-made civilisation, such as copper, the 
other heavy metals, iodine or arsenic, were distributed on the 
whole through the crustal magma only in minute proportions 
amounting to less than one part in ten thousand, or in such a pro- 
portion as would utterly prohibit our collection of them in suitable 
quantities to supply our present day necessities, were they to have 
rei n ained thus evenly d istrib i it ed . 
Fortunately for us nature is above all the great concentrator 
of her own widely dispersed wealth, this concentration being de- 
pendent to some extent upon purely physical and mechanical 
processes, but in the main upon chemical processes which it behoves 
the chemist of the present day to study closely, lest mankind, 
having rifled to exhaustion the more obvious and easily accessible 
of nature’s storehouses, shall find itself without the knowledge 
which will enable it to maintain its sources of essential supplies. 
Geochemistry, the chemistry of the earth’s crust, is not by any 
means a new science, though its name is somewhat new, but it is a 
science which has been greatly neglected in most civilised coun- 
tries-. The birth of geochemistry was in fact coincident with the 
birth of the sciences of chemistry and mineralogy, since amongst 
the first substances to be subjected to chemical analysis were some 
of the commoner minerals, and in still earlier times manufactures 
