manufactured to close tolerances. Its modulus of elasticity must be quite uniform throughout, it must be closely circular, and uniform in thickness. The glass as it is manufactured is probably uniform enough in modulus of elasticity, and the molded pyrex blanks are probably close enough to circular. Since flexure varies inversely as the cube of the thickness of the blank, the thickness must meet fairly close tolerances. It is recommended that the back of the mirror to be warped be ground flat or slightly concave or convex and the thickness of the blank at the edge should be made uniform to within about 0.001 inch.
The warping harness of Figure 2 has a fairly firm grip on the mirror. This suggests that the mirror-mounting lugs might simply be attached to the warping harness. If this is done, any adjustment of the warping harness will change the collimation of the mirror and make recollimation necessary. This is not in itself a serious objection to its use. If the mirror is to be used in a fixed position, such would be the case in a wind-tunnel application, this method of mounting the mirror is probably worth considering.
With this method of mounting, gravity acts on the mirror which, in turn exerts forces against the warping harness. Equal and opposite forces are automatically set-up in the warping harness. These will, in general, merely change all the individual forces exerted by the warping harness by an equal amount. This might throw the warping harness out of adjustment, but if the mirror is mounted this way and then adjusted, the difference in pressure will be taken care of automatically - and no one will be aware of it. If the mirror is mounted this way in a movable telescope, however, each time the telescope is pointed in a new direction, the magnitude and distribution of these forces