so that
From these various examples the following conclusions may be drawn:
1°. When a definite mesh-system has been traced on a surface and its lines numbered consecutively, every point of the surface is defined unambiguously by its two numbers (its two Gaussian numbers or co-ordinates). These numbers represent, of course, those of the respective
and
curves at whose intersection the point stands. A variation in the shape or in the numbering of the