North of that river the parallel chains of the Jura form an arc of a circle with its convexity towards the north-west.
On its southern side the plateau is bounded by the high chains of the Taurus and the Anti-Taurus, which form a crescent with its convexity facing southwards.
West of this line the rocks are chiefly Tertiary and Quaternary; east of it they are mostly Palaeozoic or gneissic. In the western mountain ranges the beds are thrown into a series of folds which form a gentle curve running from south to north with its convexity facing westward.
Either of the two is the all, as, for example, the law of the convexity of the curve is the law of the curve and the law of its concavity.
Then when once across the stream it was discovered that unlike the normal slopes in the district the hillside in front of them showed a slight convexity under cover of which they were able to re-form in regular order.
In the east a well-defined mountain system runs nearly parallel to the Black Sea coast from Batum to Sinope, forming a gentle curve with its convexity facing southwards.
The main water-parting of the Peninsula is everywhere near the edge of the table-land on the north, east and south, and hence describes a semicircle with the convexity to the east.
It forms an arc of a circle of which the convexity turns slightly to the north; neither bay nor promontory breaks the regularity of its outline.
Most of them lie near the west coast or on the islands off this coast; and they are arranged in lines which run approximately from north to south, with, generally, a slight convexity towards the west.
As this arrangement extends also to the margins, the wings are more or less twisted upon themselves and present a certain degree of convexity on their superior or upper surface, and a corresponding concavity on their inferior or under surface, - their free edges supplying those fine curves which act with such efficacy upon the air in obtaining the maximum of resistance and the minimum of displacement.