Infnisires of Lake MentphreiiKigo;/. — Marsfers. 
south consist of thinly bedded shaly limestones. These ex- 
tend on the west side as far south as Sargent's ba}', and on 
the east within a short distance of Magoon's point. The three 
islands known as the"Three 
Sisters" show admirable ex- 
posures of the same lime- 
stone series, which is re- 
garded as belonging to the 
Upper Silurian period. 
Passing to the south along 
the east shore a limestone 
formation was found to 
overlie a slaty series con- 
taining graptolitic remains. 
The slaty rocks are re- 
garded by the Canadian 
Geological Survey as Cani- 
bro-Silurian. Between the 
graptolitic slates and the 
mouth of Fitch bay was 
found a schistose slaty de- 
posit resting upon a crys- 
talline series skirting the 
north shore of Fitch bay. 
The latter is regarded by 
Mr. Ells as pre-Carabrian,* 
being an extension of the 
Sherbrooke anticline which 
gives rise to Stooke mountain to the northeast. At Magoon's 
point were found moderately fine grained granites associated 
with schistose and slaty rocks. From this point to the 
southern extremity of the lake the country rock is quite ex- 
tensively covered with drift. The granite is undoubtedly an 
outlier of the granitic series mapped by the Canadian Survey. 
Similar rocks cover quite large areas to the east and north. 
The Upper Silurian limestones on the west were found to 
extend to the north side (jf the entrance to Sargent's ba^'. 
*R. W. Ells, Rejjorl on the g»'olo<ry of a i)ortion of the oaslern town- 
ships, rolalirijr rnori' csiu'cially to lln' ooiuUies of Comittoii, Slanstead. 
Bcaiici", Richmond and Wolf"'. Can. (.icol. Survo}', Pi. J, An. Rep. 1886, 
p. 32. 
