1. The purpose of the discourse was to trace some of the influences which have produced the present external forms of the stratified mountains of Savoy, and the probable extent and results of the future operation of such influences.

The subject was arranged under three heads:—

1. (I.) The Materials of the Savoy Alps.

2. (II.) The Mode of their Formation.

3. (III.) The Mode of their subsequent Sculpture.

2. (I.) Their Materials.—The investigation was limited to those Alps which consist, in whole or in part, either of Jura limestone, of Neocomian beds, or of the Hippurite limestone, and include no important masses of other formations. All these rocks are marine deposits; and the first question to be considered with respect to the development of mountains out of them is the kind of change they must undergo in being dried. Whether prolonged through vast periods of time, or hastened by heat and pressure, the drying and solidification of such rocks involved their contraction, and usually, in consequence, their being traversed throughout by minute fissures. Under certain conditions of pressure, these fissures take the aspect of slaty cleavage; under others, they become irregular cracks, dividing all the substance of the stone. If these are not filled, the rock would become a mere heap of débris, and be incapable of establishing itself in any bold form.