THREE:A leading principle in machinery of transmission that more than any other furnishes data for strength and proper proportions is, that the stress upon the machinery, whatever it may be, is inverse as the speed at which it moves. For example, a belt two inches wide, moving one thousand feet a minute, will theoretically perform the same work that one ten inches wide will do, moving at a speed of two hundred feet a minute; or a shaft making two hundred revolutions a minute will transmit four times as much power as a shaft making but fifty revolutions in the same time, the torsional strain being the same in both cases.We have seen how Plotinus establishes the spiritualistic basis of his philosophy. We have now to see how he works out from it in all directions, developing the results of his previous enquiries into a complete metaphysical system. It will have been observed that the whole method of reasoning by302 which materialism was overthrown, rested on the antithesis between the unity of consciousness and the divisibility of corporeal substance. Very much the same method was afterwards employed by Cartesianism to demonstrate the same conclusion. But with Descartes and his followers, the opposition between soul and body was absolute, the former being defined as pure thought, the latter as pure extension. Hence the extreme difficulty which they experienced in accounting for the evident connexion between the two. The spiritualism of Plotinus did not involve any such impassable chasm between consciousness and its object. According to him, although the soul is contained in or depends on an absolutely self-identical unity, she is not herself that unity, but in some degree shares the characters of divisibility and extension.447 If we conceive all existence as bounded at either extremity by two principles, the one extended and the other inextended, then soul will still stand midway between them; not divided in herself, but divided in respect to the bodies which she animates. Plotinus holds that such an assumption is necessitated by the facts of sensation. A feeling of pain, for example, is located in a particular point of the body, and is, at the same time, apprehended as my feeling, not as some one elses. A similar synthesis obtains through the whole of Nature. The visible universe consists of many heterogeneous parts, held together by a single animating principle. And we can trace the same qualities and figures through a multitude of concrete individuals, their essential unity remaining unbroken, notwithstanding the dispersion of the objects in which they inhere.
