slaty cleavage appears in some instances to have originated 
joints by which the rock is broken up into rhomboidal 
forms.” 
In the Geologist for May, 1862, Mr. Thomas Grindley 
describes these deposits as Lower Cambrian, and states that 
few organic remains had been met with in them, except 
some imperfectly preserved fucoids and corals, and he 
estimates the thickness of the strata from 7 to 10,000 feet. 
In vol. iv., p. 71, of the Transactions of the Manchester 
Geological Society, Mr. John Taylor, F.G.S., describes the 
Manx schists as of Cambrian age, and states that in the 
quarries below the Castle Mona Hotel, Douglas, he had 
discovered both fucoids and the tracks or castings of 
worms. 
Professors Harkness and Nicholson, in a paper printed in 
the Quarterly Journal, vol. xxii., p. 488, come to the con- 
clusion that the Manx schists are of Silurian age, and consist 
of green slates and porphyries, and Skiddaw slates, and in 
confirmation of their opinion as to the latter deposits, state 
that they had found, on the north of Douglas Bay, specimens 
of Palceochorda major. 
Mr. John Horne, F.G.S., of the Geological Survey of 
Scotland, in a memoir printed in vol. ii., part iii. of the 
Transactions of the Geological Society of Edinburgh, in 
writing on the Silurian rocks of the island, states “tliat nearly 
four-fifths of the island are made up of rocks belonging to 
this formation. A chain of high ground extends from Kamsay 
to the Call* of Man. This chain, running from N.E. to S.VY., 
forms the backbone of the island, and is approximately the 
strike of the Silurian rocks. These rocks, so far as observed 
by me, consist of indurated grey slaty shales and flags. In 
many places they show imperfect cleavage. In Glen Moar, 
and on Slieu Dhoo, in the Sul by Glen and its tributaries, and 
on the top of Snaefell, the general dip varies from 20° to 40^ 
N. of W. Again, in the south of the island, in Silver Burn, 
