commonly people have been content to follow the well-trodden path marked out by Lanz.[1]
In Italy, Ampère's seed has also taken root. In the Cinematica applicata alle arti, a text-book for technical schools, which first appeared in 1847 under a somewhat different title, Giulio has left to his country a valuable gift. This book unites admirably Kinematics and Mechanics; it follows Willis pretty faithfully in essentials, but not without an attempt,—incompletely successful,—to replace the hydraulic machines which Willis had struck out. A delicate intellectual inspiration breathes through the whole work, and is the more notable that it was written for pupils not having more than an elementary acquaintance with mathematics. The concise mathematical expressions, which speak for themselves, have thus had to be replaced by explanations in words,—a method which presupposes a deeper understanding on the part of the author than is shown in many books bristling with formulæ.
In 1849, Laboulaye, again in accordance with Ampère's suggestion, attempted in his Cinématique to set forth the science of Mechanisms in a complete form. He also discards Willis' limitation of mechanisms to those constructed of rigid bodies, and points out also that Ampère required something impossible in wishing absolutely to exclude the consideration of force from Kinematics. Besides this he attempts to determine a new theoretical method of a general character. This consists in dividing the whole "machine-elements" into three classes, which he calls système levier, système tour, and système plan, corresponding respectively to the making fixed (inébranlables) for the time, one, two, or three and more points of the moving body. These "systems," however, do not really cover the problem, of which we shall find the proof in its proper place. Even their originator has not made any real use of them, feeling, doubtless, that there was not much to be gained by doing so. So far as applied Kinematics is concerned, he seems rather to return to the system of Lanz, with suitable subdivisions. Indeed, he goes so far in this direction as to construct Monge's system a priori, thus showing that it forms, in
- ↑ Since the first publication of these remarks the second edition of Prof. Willis' work has appeared. (London 1870.) It is considerably in advance of the first, but in all essential points the principles originally laid down are unchanged. It so far confirms my view that the author, while retaining his original divisions and subdivisions, has inverted their order. R.
