epochs in the history of the globe received its name.  It was in a deep gorge of the Jura, that, more than half a century ago, Leopold von Buch first perceived the mode of formation of mountains; and it was at the foot of the Jura, in the neighborhood of Neufchatel, that the investigations were made which first led to the recognition of the changes connected with the Periods.  As I shall have occasion hereafter to enter into this subject more at length, I will only allude briefly here to the circumstances.  In so doing I am anticipating the true geological order, because I must treat of the Jurassic and Cretaceous deposits, which are still far in advance of us; but as it was by the study of these deposits that the circumscription of the Periods, as I have defined them above, was first ascertained, I must allude to them in this connection.

Facing the range of the Jura from the Lake of Neufchatel, there seems to be but one uninterrupted slope by which it descends to the shore of the lake.  It will, however, be noticed by the most careless observer that this slope is divided by the difference in vegetation into two strongly marked bands of color:  the lower and more gradual descent being of a lighter green, while the upper portion is covered by the deeper hue of the forest-trees, the Beeches, Birches, Maples, etc., above which come the Pines.  When the vegetation is fully expanded, this marked division along the whole side of the range into two broad bands of green, the lighter below and the darker above, becomes very striking.  The lighter band represents the cultivated portion of the slope, the vineyards, the farms, the orchards, covering the gentler, more gradual part of the descent; and the whole of this cultivated tract, stretching a hundred miles east and west, belongs to the Cretaceous epoch.  The upper slope of the range, where the forest-growth comes in, is Jurassic.  Facing the range, you do not, as I have said, perceive any difference in the angle of inclination; but the border-line between the two bands of green does in fact mark the point at which the Cretaceous beds abut with a gentler slope against the Jurassic strata, which continue their sharper descent, and are lost to view beneath them.

This is one of the instances in which the contact of two epochs is most directly traced.  There is no question, from the relation of the deposits, that the Jura in its upheaval carried with it the strata previously accumulated.  At its base there was then no lake, but an extensive stretch of ocean; for the whole plain of Switzerland was under water, and many thousand years elapsed before the Alps arose to set a new boundary to the sea and inclose that inland sheet of water, gradually to be filled up by more modern accumulations, and transformed into the fertile plain which now lies between the Jura and the Alps.  If the reader will for a moment transport himself in imagination to the time when the southern side of the Jurassic range sloped directly down to