Around Saganaw Bay the prim- itive formation appears to approach nearer the surface; the secondary limestone then gives place to sandstone, which disinte- grates, and forms sand banks and beaches, as on the sea shore.

With the exception of spots of sand op- posite the mouth of Spanish and other rivers, the shore of Lake Huron is composed of naked rocks ; but on the , and at the naval station of Penetanguishine, there are several undulating alluvial plat- forms some hundred feet high, rounded into knolls, intersected by water-courses, and extending to the N.

W shores of Lake Simcoe, and, in fact, to Lakes Erie and Ontario.

Mr A.

Murray, in his elaborate geological survey of the shores of Lake Huron, says, that the older groups he observed, consist, firstly, of a metamorphic series, composed of granitic and sienitic rocks, in the forms of gneiss, mica slate, and hornblende slate; and, secondly, of a stratified series, com- posed of quartz rock, or sandstones, or con- glomerates, shales, and limestones, with interposed beds of greenstone; and of the fossil iferous groups following these, six for- mations are met with, which, in the New York nomenclature, come under the follow- ing designations : 1.