The contour lines showing the heights above sea-level are the directions along which species spread to form zones.
The average elevation of the east boundary is about 850 ft., while contour lines of3500-3900ft.
Contour lines (isobaths) were introduced for the first time on a chart of the Merwede by M.
While all wings are graduated as explained, innumerable varieties occur as to their general contour, some being falcated or scythe-like, others oblong, others rounded or circular, some lanceolate and some linear.
All these things were, in their varying degrees, elements of policy upon which the Allied strategy must base itself if its war aims were to be obtained, and accordingly the military treaty between Bulgaria and Serbia provided for a Serbo-Bulgarian army of 7 Serbian and 3 Bulgarian divisions to invade Macedonia, moving concentrically against the front Uskub - Kumanovo - Kratovo - Kochana, forming the outer contour of the plain known as Ovche Polye which was assumed on both sides to be the natural concentration area of the Turks.