218 



THE GEOLOGIST. 



dred and fifty-five to three liimdred and fifty-two feet in tieiglit above 

 tlie level of the lake. At that part of the island near Manitonwaning 

 there is a lake of an hour-glass shape, possessing an area of fifty-five 

 square miles (the area of the whole island is sixteen hundred square 

 miles), associated with which there is a peculiarity, especially 

 described by Mr. Murray. He found that this lake was one hundred 

 and fifty- five feet above Lake Huron, and the " question of interest 

 connected with this lake, which constitutes its peculiarity, is the 

 source whence it derives its supply of water." Mr. Murray found 

 but one small stream to be its visible supply ; and although thus 

 receiving so scanty a tribute from the surrounding country, it fur- 

 nished water for three large brooks, which fall from it to the south, 

 the west, and the north. These supply several lakes, ponds, and 

 streams, among others, Tecumseth Lake, the level of the water in 

 which was found in the early part of August to have been much 

 higher than it must have been in the spring or some later period. 

 This great island consists chiefly of the ISTiagara limestones ; and as 

 this is known frequently to give subterranean passage to streams, 

 Mr. Murray thinks it probable that such a communication may exist 

 between these lakes, and that there may be others in connection with 

 them, and thus the water of Tecumseth Lake may arise from the 

 drainage of a considerable part of the island. 



It is possible that further investigation may develope some inter- 

 esting facts in relation to these subterranean communications, and 

 lead to the discovery of actual caverns. It is earnestly hoped that 

 the labour of investigation may be undertaken by persons residing on 

 the island. 



29. — Murray's Cavern and Subterranean River, Ottawa, (See 



Map, pi. X. 



This very singular cavern exists at the fourth chute of the Bonne 

 Chere river, one of the tributaries of the Ottaway river, recently ex- 

 plored by Mr. Murray, of the Canada Geological Survey. At the 

 chute a portion of the water turns abruptly ofi* at right angles to the 

 general course, running northerly for about ten chains through a 

 great cavern formed in the Trenton limestone of the Lower Silurian 

 formation. Mr. Murray describes the cavern as naturally nearly dry, 

 except during freshets. Mr. C. Merrick, an enterprising proprietor 

 of the cave and its vicinity, has caused a dam to be thro^vn across 

 the main body of the stream, near the middle of the chute, which 

 turns a sufficient quantity of water through to convert the channel 

 into a mill-race, and the fall from the lower end is thus advan- 

 tageously applied to drive the water-wheel of his mill.* The strata 

 of limestone and shale exposed near Mr. Merrick's mill are in all 

 forty-six feet thick, and well charged with fossils, of which Mr. Bil- 

 lings gives a list of sixteen Trenton, four Black river, one Bii'dseye, 



* Geological Survey of Canada, Report for 1853, p. 77. 



