40 
Ancient lake and river-beds of a similar kind ax% 
common in Perthsbire. It may have been that the 
Grampians at one time formed a natural barrier at 
Dunkeld; and the Ochils and Sidlaws at Perth, 
damming up ancient lakes, whose waters subse¬ 
quently found exit towards the sea by rupture or 
erosion at the Pass of Birnam, and between Moncreiffe 
and KinnouU Hills at Perth, In Glenshee and many 
of the minor valleys of Perthshire “flats ” of gravel 
and sand occur, presumably auriferous. Also pro¬ 
bably auriferous are former river-beds—for example, 
those of the very errant and fickle Tay herself. The 
beds of many of the Perthshire rivers have a struc¬ 
ture closely resembling that of the so-called Riverine, 
gold fields of Otago and British Columbia; while 
the terraces—of water-worn shingle—to be found in 
many of the Perthshire mountain-valleys, and which 
mark the varying levels of the ancient lakes, are ap¬ 
parently the equivalents of the “benches” of British 
Columbia. 
Though most commonly found in connection with 
Silurian i’ocks, gold is, hov/ever, by no means con¬ 
fined thereto ; for Sir Charles Lyell, in his Elementury 
Manuel of Geology, points out that “ gold has now 
been detected in almost eve > y kind of rock I” Whence 
it may be inferred that, while gold is most likely to 
occur in the Silurian area of Perthshire, it may occur 
in any part of the county, lov/land as well as highland ! 
IV. The Minerals, with ^yhich gold is gene¬ 
rally ASSOCIATED, ABOUND IN PERTHSHIRE. 
These minerals are especially the Metallic Sulphides 
—of iron and lead-in vein stuflfs of quartz, and cal¬ 
careous or heavy spars. At Tyndrum, for instance, 
lead occurs—and is mined—in mica slate near its 
junction vdth quartz rock (Nicol) ; and a reference 
to Nicol’s Geology of Scotland will show that metal¬ 
liferous veins are frequent in the Silurians of the 
Perthshire Highlands. These metalliferous deposits 
are most common in connection with penetration of 
the slates by intrusive masses of greenstone, por¬ 
phyry, or other trap rocks ; and the latter are fre¬ 
quent in Perthshire—e.p., in the basin of Loch Tay, 
