razor's edge, which arise from improper tempering and lack of skill in working, are usually so minute, that they may remain undistinguished until the razor is used. They will nevertheless very sensibly add to the friction the razor produces on the skin and particularly if it happens to be thin and tender. There are two ways of judging of the temper of a razor; one of these is practically infallible—viz:—the examination of the blade and its edge by means of a microscope.
It will be readily admitted that the real excellence of a razor is in direct proportion to the firmness and unbroken regularity of its edge. When a razor is too brittle, in consequence of having been either to much heated in the process of hardening, or not sufficiently cooled in that of tempering, it cannot possibly take a good cutting edge, no matter how much skill may be employed in honing and stropping it. Such defects are quickly detected by the use of a micro-
