GIBB — ON CANADIAN CAVERNS. 
217 
of the river Speed, near Mr. Strange's mill. It extends under the 
cliff for between thirty and forty yards, and is about the same in 
width at its mouth ; the 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 Niagara limestones. It is highly important that the attention of 
scientific men in Canada should be dii'ected to the subject of their 
discovery and investigation, at the same time making careful search 
for the bones of animals. 
27. — Cavern in the Bat Islands, Lake Erie. 
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. — SUBTBRRASTEAN PASSAGES IN THE GrEAT MaNITOULIN ISLAJTD, 
Lake Huron. 
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 vdth 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- 
* Jour, of Science and Arts, vol. iv. : 1828. 
t Geological Survey of Canada, Report of Progress for 1847-8. 
VOL. III. 2 E 
