Makch 28, 1913] 



SCIENCE 



465 



enteenth century. Just how commerce and 

 industry led up to, and prepared the way 

 for, this step is the subject of a most inter- 

 esting chapter by a member of this acad- 

 emy, Professor Mann.' 



Without underestimating the contribu- 

 tions of Pappus or Tartaglia or Benedetti 

 or Stevinus or Leonardo da Vinci, to me- 

 chanics; and without denying the impor- 

 tant role of statics in architecture and in 

 other structural work, one may, I believe, 

 fairly say that the years which intervene 

 between Archimedes and Galileo are prac- 

 tically barren of progress in physics. 



It is true, indeed, that during this in- 

 terval a large number of isolated physical 

 facts had been discovered; indeed, there is 

 scarcely a chapter in physics in which some 

 advance of this type can not be mentioned ; 

 but, during all this while, nothing in the 

 way of development is seen; individual 

 discoveries remain isolated; they do not 

 bear fruit; speculation and guessing were 

 still employed where we use observation 

 and measurement and computation. 

 Leonardo da Vinci likens a scientific con- 

 quest to a military victory in which theory 

 is the field marshal; experimental facts, 

 the soldiers. The philosophers who pre- 

 ceded Galileo had, in the main, been try- 

 ing to fight battles without soldiers. The 

 only possible exceptions to this statement 

 are Roger Bacon, Leonardo da Vinci, 

 Stevinus and Gilbert. They had measured 

 some mechanical quantities — a few of them 

 — masses and stresses — such as could be 

 obtained by means of a steel-yard and a 

 measuring stick; but they were still in the 

 domain of statics. Now from a geomet- 

 rical, esthetic or even utilitarian stand- 

 point it is difficult to imagine any finer 

 subject than graphical statics; and yet 

 when we regard the progress of physics, 



'Mann, "Teaching of Physics," pp. 107-110 

 (Macmillan, 1912). 



statics is to dynamics somewhat as osteol- 

 ogy is to physiology, a veritable vaUey of 

 dry bones. The live part of mechanics is 

 kinetics, the study of masses which are in 

 motion, the consideration of bodies which 

 are changing their velocities, currents of 

 water, oscillating magnets, vibrating 

 strings, rotating wheels, electric motors, 

 heat engines, electromagnetic waves, and 

 X-rays. These are the problems over 

 which men lose sleep; these are the ques- 

 tions which compel the interest of the 

 physicist; these are the subjects whose mas- 

 tery confers power upon the engineer. 

 The one confessed aim of physical science 

 is, indeed, to describe the motion of bodies 

 in the simplest possible manner. Indeed, 

 it is only by the aid of this modern science 

 of the energy of motion that any of the 

 ancient mechanical doctrines — such as the 

 atomic theory of Democritus — have ac- 

 quired validity; it is this same science 

 which has rendered the heliocentric theory 

 of Copernicus not merely "a plausible 

 view" but the one possible view. 



We pass now to a more definite ques- 

 tion, namely, what contribution did "our 

 Academician" make to the solution of 

 problems of this type, to the science which 

 now goes by the name of physics? To 

 answer briefly and baldly, he instituted the 

 method and set into motion the machinery 

 by which practically all these problems 

 have been solved, in so far as they have 

 been solved at all. But lest I give the 

 false impression that Galileo was the an- 

 cestor of all the physical sciences, I hasten 

 to a more detailed answer of the query, 

 What did Galileo? 



1. First, no greater mistake could be 

 made than to suppose that Galileo was the 

 first man to differ with Aristotle; the 

 academy of Cosenza, having opposition 

 to the peripatetic philosophy as its avowed 

 purpose, was established at Naples about 



