fome Strata in Ireland and Scotland. ty 
from the Mull of Kinhouth, the eaftern fide, being hornftone 
till near M‘ Arthur’s Head ; and from thence, round to the weft- 
ward, the cliffs being of chert. Continuing the route for 
almoft a mile along the high road, after leaving the limeftone, 
veins of fliale, and of a whitilh ftone marl, are feen ; then 
the chert appears, which reaches to Port Aflteg, and north and 
fouth from thence along the fhores of the found not only on 
the Ilay but likewife on the Jura fide. Within the ifland are 
feveral fmall lochs (or lakes) and many turf mofles. Where 
the limeftone prevails are fome minute ftrings of rich copper 
ore, and mines are opened in lead ore veins y but they are not 
productive of profit to the adventurers. There are many old 
workings, fuppofed to have been opened by the Danes. Iron 
ore is found ftratified in the mountains. Bog iron ore is met 
with in the mofles , and near Bally-echra is a body of form 
iron ore. At Loch Knock, near M‘Arthur’s Head, is an 
"extenfive bed of gneifs ; and near Ardleftree is an immenfe 
Whyn Dyke, and the hill Knock Reneftle is a magnetic 
mafs of rock, which confiderably deranges the compafs, as you 
difcovered when you vifited it laft fummer. 
The Whyn Dykes are too fingular in their formation to 
efcape the eye of the naturalift who traverfes this ifland. Thev 
are mafles, or rather veins, generally of a dark-brown (appa- 
rently bafaltic) matter, not unfrequently containing bladder- 
holes ; from three, four, and fix feet, to eight or more yards 
in breadth, running in various directions. In fome places they 
are ftraight for a confiderable length ; in others, their courle, 
though progreflive, is infleCted ; and in fome parts they rife 
between three and four feet above the furface, forming natural 
boundaries or dykes (from whence their name feems to be 
\ ol. LXXX. N derived) 
