GIBB — ON CANADIAN CAVEENS. 



217 



of tlie river Speed, near Mr. Strange's mill. It extends under tlie 

 cliff for between tMrty and forty yards, and is abont the same in 

 widtb at its moutb ; tbe roof, from five to six feet in height at the 

 entrance, slopes towards the floor inwards, and at the termination of 

 the distance specified, the space becomes insufficient to permit of a 

 man's body to pass, so that the extent of the cavern beyond is un- 

 known ; the roof and floor are studded with small stalactitical in- 

 crustations. 



The account given of these two caverns is meagre enough, but 

 several others are known to exist, although they are not described ; 

 their dimensions, however, are large, and it is probable that a dis- 

 tinct and important series of caverns pervade almost the whole of 

 that part of the peninsula of western Canada, which is traversed by 

 the Magara limestones. It is highly important that the attention of 

 scientific men in Canada should be directed to the subject of their 

 discovery and investigation, at the same time making careful search 

 for the bones of animals. 



27. — Caveen in the Bat Islands, Lake Eeie. 



The Bass Islands, two in number, lie some miles to the south-west 

 of Point Pele island, at the western end of Lake Erie, and are formed 

 of the superior group of the Helderberg series of rocks, which con- 

 stitute the base of the Devonian system. In one of these islands is a 

 cavern, which is entered by a round hole, a yard in diameter, gra- 

 dually widening for fifty feet, when it opens into a circular space, 

 one hundred feet in diameter, and seven feet high. The roof is 

 studded with brown stalactites, frequently hollow, and seldom more 

 than three-fourths of an inch thick, or longer than three inches. 

 The floor is covered with stalagmite. This description was furnished 

 to Dr. Bigsby when near this place in 1819, by Lieut. Dix, aide -de- 

 camp to the American General Brown.* Dr. Bigsby was shown 

 several conical stalactites from this cavern at Moy, opposite to De- 

 troit ; they were ten inches long, by seven inches broad at their base. 

 It seems to me not improbable that this cave was much higher at 

 one time, and that the greater part of the roof consists of a great 

 thickness of the stalactitical carbonate of lime. 



28. — Subteeeanean Passages in the Geeat Manitoulin Island, 



Lake Hueon. 



This very large and beautiful island forming the northern boundary 

 of Lake Huron, with a length of eighty, and average breadth of 

 twenty miles, is well covered with streams and lakes. A series of 

 bold escarpments run longitudinally through the whole length of the 

 island, and are described by Mr. Murrayf as varying from one hun- 



* JoTir. of Science and Arts, vol. iv. : 1828. 

 t Geological Survey of Canada, Report of Progress for 1847 -8. 

 VOL. III. 2 E 



