CHAPTER II 



SPACE 



Its Measurement and Representation by 

 Photography 



Summary. — Tendency to replace outline drawings, plans, and diagrams 

 in relief by photography — Photography traces the various positions 

 in space occupied by a moving body — Photographic trajectory 

 of the movements of a point in space ; its stereoscopic trajectory 

 — Movements of a straight line in space — Solid figures formed 

 thereby : cylinders, hyperboloids, cones, etc. — Movements of a 

 curve in space ; photography < f the figures which it forms : 

 spheres, ellipsoids, etc. — Stereoscopic pictures of figures of three 

 dimensions — Figures formed by the movement of solid bodies; 

 effects of light and shade. 



Tendency to replace Outline Drawings, Plans, and 

 Diagrams in Relief by Photography . —The positions of 

 bodies in space, their forms and dimensions, find 

 their natural expression in geometrical drawings. Such 

 drawings, executed to a known scale, supply all the 

 information that is required. 



During the last few years, however, there has been 

 a tendency to substitute photography for outline 

 drawings, and doubtless in the future it will completely 

 replace them. Indeed, it supplies with remarkable 

 ease pictures of undoubted accuracy. The dimensions 

 can be enlarged or reduced as occasion may require., 

 and if thought desirable, a scale for the purpose of 

 measurement may be introduced, into the picture, and 



