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  be classed by themselves, as is done by Poncelet,—still the principle is not carried sufficiently far, for under this title all machines of every kind must be treated, which, however, has not been the case. Redtenbacher first removed this stigma of indistinctness from the matter, and thereby laid the foundation of the freshness and power which the German system of machine-instruction shows as contrasted with the French. Redtenbacher's most lasting services, which have not always been, understood by his successors, lie in this direction,—in the separation of the questions connected with machinery into separate sciences or branches of science. It was on this ground that his influence was, I may say, so electric; and brought to him so quickly in his time the engineering students of Germany.

The existing treatment of the theory of machines (theoretische Maschinenlehre) confines itself principally to prime-movers,—Steam-engines, Water-wheels, Turbines, Windmills, and so on,—or in terms of our definition, it concerns itself. Yet it does also consider machines in general (other than prime-movers), and obviously these all belong to its province. To the general examination of the theory of these machines the name is often given. This is not universal, nor indeed is it correct, for mechanical technology must include all mechanical processes of manufacture, and in a multitude of cases machines are not employed in these. It possesses therefore a domain of its own, and must be treated in its own proper way. From its own point of view it also examines the machine, but in a way entirely differing from that in which it is examined for its own sake in the studies of which we are speaking. While therefore it can easily be understood how both studies should set up claims to the same object of instruction, it is on that very account important that they should not be confused with each other.

The special part of technology here coming into question,—or what may be called the technological part of the study of special machines,—concerns itself with the action of the natural forces, through their various applications in the machine, on the bodies to be worked upon. It examines, in other words,