THREE:His analysis of individuality was the first step in this direction. We have seen that he treats definition as a process of gradual specification, beginning with the most general notions, and working down by successive differentiations to the most particular. Now, the completed conception is itself the integration of all these differences, the bond of union holding them together. Turning to an antithetical order of ideas, to the material substance of which bodies are composed, and its various transformations, we find him working out the same vein of thought. According to the Aristotelian chemistry, an ultimate indeterminate unknowable something clothes itself with one or other of the opposing attributes, dry and moist, hot and cold; and when two of these are combined, manifests itself to our senses as one of the four elements. The elements combine in a particular manner to form homogeneous animal tissues, and these again are united into heterogeneous organs, which together constitute the living body. Here, then, we have two analogous series of specificationsone conceptual and leading down from the abstract to the concrete, the other physical, and leading up from the vague, the simple, and the homogeneous, to the definite, the complex, and the heterogeneous. Aristotle embraces both processes under a single comprehensive generalisation. He describes each of them as the continuous conversion of a346 possibility into an actuality. For the sake of greater clearness, let us take the liberty of substituting modern scientific terms for his cumbrous and obsolete classifications. We shall then say that the general notion, living thing, contains under it the two less general notionsplant and animal. If we only know of any given object that it has life, there is implied the possibility of its being either the one or the other, but not both together. On determining it to be (say) an animal, we actualise one of the possibilities. But the actualisation is only relative, and immediately becomes the possibility of being either a vertebrate or an invertebrate animal. The actuality vertebrate becomes the possibility of viviparous or oviparous, and so on through successive differentiations until we come (say) to a man. Now let us begin at the material end. Here are a mass of molecules, which, in their actual state are only carbon, nitrogen, and so forth. But they are potential starch, gluten, water, or any other article of food that might be named; for under favourable conditions they will combine to form it. Once actualised as such, they are possible blood-cells; these are possible tissues; these, again, possible organs, and lastly we come to the consensus of vital functions, which is a man. What the raw material is to the finished product, that are the parts to the entire organism, the elements to the compound, the genus to the species, and such in its very widest sense is potency to realisation, δ?ναμι? to ?ντελ?χεια, throughout the universe of growth and decay.246Presuming an engineering establishment to consist of one-storey buildings, and the main operations to be conducted on the ground level, the only vertical lifting to be performed will be in the erecting room, where the parts of machines are assembled. This room should be reached in every part by over-head travelling cranes, that cannot only be used in turning, moving, and placing the work, but in loading it upon cars or waggons. One result of the employment of over-head travelling cranes, often overlooked, is a saving of floor-room; in ordinary fitting, from one-third more to twice the number of workmen will find room in an erecting shop if a travelling-crane is employed, the difference being that, in moving pieces they may pass over the top of other pieces instead of requiring long open passages on the floor. So marked is this saving of room effected by over-head cranes, that in England, where they are generally employed, handling is not only less expensive and quicker, but the area of erecting floors is usually one-half as much as in America, where travelling-cranes are not employed.