As to the modes in which invention manifests itself, Mr. William H. Smyth says:--“Examine at random any one of half a dozen lines of mechanical invention, one characteristic common to them all will instantly arrest attention--they present nothing more than a mere outgrowth of the manual processes and machines of earlier times. Some operation, once performed by hand tools, is expedited by a device which enables the foot as well as the hand to be employed. Then power is applied; the hand or foot operation, or both, are made automatic, and possibly, as a still further improvement, several of these automatic devices are combined into one. All the while the fundamental basis is the old, original hand process; hence, except in the extremely improbable event that this was the best possible method, all the successive improvements are simply in the direction, not of real novelty, but of mere modification and multiplication. The most important and radical departures from old methods, by which many of the industries of the world have been completely revolutionized, are nearly always originated by persons wholly ignorant of the accepted practice in the particular industry concerned. The first and most important prerequisite to invention is an absolutely clear insight into, and a comprehensive grasp of, all the conditions involved in the problem. A scheme for the cultivation of invention should in part include:--(1) Accurate and methodical observation. (2) Cultivation of memory and the faculty of association. (3) Cultivation of clear visualization. (4) Logical reasoning from actual observation. The course should include exercises in drawing from simple objects, and the solution of a simple problem, such as that of a can-soldering machine.” The Debt to Research in Medicine. Investigators are never so useful as when thoroughly disinterested; let them find what they may, it will either have worth in itself or lead to something which has. Dr. Pye-Smith says:--