THREE:"Wait! wait! wait!"
THREE:Platens as a rule run back at twice the forward or cutting movement, and as the motion is uniform throughout each stroke, it requires to be stopped at the extremes by meeting some elastic or yielding resistance which, to use a steam phrase, "cushions" or absorbs the momentum, and starts the platen back for the return stroke.
THREE:We must now bring this long and complicated, but it is hoped not uninteresting, study to a close. We have accompanied philosophy to a point where it enters on a new field, and embraces themes sufficiently important to form the subject of a separate chapter. The contributions made by its first cultivators to our positive knowledge have already been summarised. It remains to mention that there was nothing of a truly transcendental character about their speculations. Whatever extension we may give to that terrible bugbear, the Unknowable, they did not trespass on its domain. Heracleitus and his compeers, while penetrating far beyond the horizon of their age and country, kept very nearly within the limits of a possible experience. They confused some conceptions which we have learned to distinguish, and separated others which we have learned to combine; but they were the lineal progenitors of our highest scientific thought; and they first broke ground on a path where we must continue to advance, if the cosmos which they won for us is not to be let lapse into chaos and darkness again.
TWO:It may be remarked as a general rule that the hardness of cutting tools is "inverse as the hardness of the material to be cut," which seems anomalous, and no doubt is so, if nothing but the cutting properties of edges is considered; but all cutting edges are subjected to transverse strain, and the amount of this strain is generally as the hardness of the material acted upon; hence the degree of temper has of necessity to be such as to guard against breaking the edges. Tools for cutting wood, for example, can be much harder than for cutting iron, or to state it better, tools for cutting wood are harder than those usually employed for cutting iron; for if iron tools were always as carefully formed and as carefully used as those employed in cutting wood, they could be equally hard.
TWO:55