ABSTRACT
The book begins with generalities, remarking how, in the case of natural occurrences, we marvel at those of which we do not know the cause, and again we marvel when arts directed to the service of mankind appear to win a victory over nature; for nature’s action is always uniform and unchanging, whereas our requirements from time to time vary in all sorts of ways. Hence, in order to produce some particular utility, we have to do something ‘contrary to nature' or ‘out of the natural order’ (7rapd <j>voiv), and for this purpose to resort to art (tc'x^). The particular art that constantly helps in such cases is the mechanical, which we call by a name derived from IM7)x<urf, a ‘contrivance’, a mechanical device, a machine. The commonest problems of a mechanical kind are those connected with the use of the lever. It seems strange that we should be able to move a great weight by applying only a small force; yet this is possible with the help of a lever, although the lever itself adds a little more weight.
