1 G 
river, and underground waters* but not so the potash. In the 
average of all these waters the ratio of potash to soda is only some- 
thing like 1 to 30, whilst in the lithosphere as a whole, the soda 
only exceeds the potash in the proportion of 11 to 10. A prolonged 
and careful investigation of this problem has led to the conclusion 
that the greater part of the naturally dissolved potash slowly re- 
combines with the kaolin and halloysite of sedimentary beds form- 
ing sericite. In the newer shales there is but little sericlte and 
chlorite and much kaolin and halloysite ; in the older ones more 
sericite and chlorite and correspondingly less kaolin and halloy- 
site ; in the oldest ones there is neither kaolin nor halloysite, their 
place being taken by sericite, and to a less extent by chlorite. It 
appears from this investigation that the essential difference be- 
tween shale and slate is not one of physical structure but the far 
more fundamental one of chemical and mineral composition. A 
slate is in fact to be defined as a shale altered by the complete or 
almost complete conversion of original kaolin and halloysite into 
sericite and chlorite. The practical application of these ’results 
to the problem of potash supply lies in the knowledge obtained 
that the greater part of the potash dissolved during rock weathering 
is permanently lost to mankind, as it would be hopeless to attempt 
to extract it from slates. The balance of this potash is to be sought 
in deposits of glauconite, alimite, jaroshe, and a few lesser known 
minerals, many of which are undoubtedly more abundant than 
has hitherto been supposed. 
The discussion of the utilisation of other sources of potash 
than those of the German mineral salts upon which we have be- 
come so dependent, raises the general question of what may be 
called the metallurgical interest of the chemist in Nature s chemicals, 
that is to say, the interest which should be taken in the study of 
the chemistry of the minerals of the earth’s crust with a view r to 
converting them more readily and more economically into the 
commercial products necessary for our every day life. One might 
be tempted to say at first sight that the cyanide process has led to 
such a convenient and cheap means of extracting gold from its 
ores, that here at least there is no room for experimentation. Yet 
we know’ that gold millers raise increasing complaints regarding the 
cost of treatment, and so long as cyanide remains a comparatively 
high priced chemical, and so long as no solution to the problem oi 
preventing the large destruction of cyanide by such common 
associates of gold as arsenopvrite, iron sulphates and copper car- 
bonates, there is ample room for the mineral chemist to work a 
revolution in the wet extraction of gold. 
At a later stage T shall refer somewhat more fully to the sources 
of our natural supplies of phosphorus. The metallurgical aspect 
appeals to us in the case of this substance. A somewhat recent 
paper* on the phosphates of Florida read before the American 
*J, A. Baw: “Use of Low Grade Phosphates, 
