39 
Calvert’s ** Gold Rocks of Great Britain and Ireland,” 
published in 1853. Moreover, information on this, 
as well as on other heads of this inquiry, occurs in 
the ‘‘New Statistical Account of Scotland ”—quoad 
at least the Highland parishes of Perthshire. 
III. The physical conpighkation and geologi¬ 
cal BASIS OF THE GPvEATER PART OF PERTH¬ 
SHIRE ARE NOT ONLY THE SA]\IE AS THOSE OF 
AVOWEDLY AURIFEROUS COUNTIES IN SCOT¬ 
LAND; BUT OP HIGHLY AURIFEROUS FOREIGN 
COUNTRIES, SUCH AS NeW ZEALAND. 
The most commonly auriferous rocks are the lower 
Silurian slates, as these are typified in our Grampians; 
and it is in the debris of these slates—the result 
mostly of denudation by ice, water, and weather, 
and of subsequent assortment by water—that alluvial 
gold occurs in all auriferous countries. 
Before I go further, let me explain that, wRere not 
otherwise specified, I am writing only of alluvial, 
or drift gold: of deposits, that is, of the metal in its 
water-worn condition, contained in the debris of the 
rocks in which it was originally embedded. It would, 
I fear, only confuse my hearers, and complicate my 
subject were I to do more here than merely refer to 
gold in situ —in its matrix—in the quartzites, which 
penetrate the schists of the Breadalbane and other 
Highland districts. 
In the highly auriferous province of Otago, New 
Zealand, the most extensive gold-deposits are the 
beds of former lakes, estuaries, or rivers, which now 
form plains or terraces, occupying present valleys. 
In these lake or river-beds there has been, during 
long ages, a deposition of the debris resulting from 
the disintegration of the auriferous slates that formed 
the ancient mountain-summits. In these former lakes 
and rivers there has been a natural sluicing, sifting, 
sorting of material, and consequent concentration of 
the gold therein contained. This material now con¬ 
stitutes gravel or shingle, clay, loam, or sand, 
variously intermixed or interbedded, cut through by 
the channels of more recent, or altogether modern 
and existing, rivers and streams. 
