1 8 Wilde, Evolution of the Mental Faculties. 



viva, in marked contradiction to those of Schopenhauer and 

 Dr. Lardner, were given by Joule in the course of a lecture 

 delivered in 1847/' in which he states that, "a bullet fired 

 from a gun at a certain velocity will pierce a block of 

 wood to only one quarter of the depth it would if propelled 

 at twice the velocity, and that four times the weight of 

 powder would be required in the latter case than in the 

 former." Thus, also, a railway train going at 70 miles per 

 hour possesses 100 times the impetus, or living force, that 

 it does when travelling at 7 miles per hour. 



The latter illustration was fully confirmed by Fairbairn, 

 who brought before this Society, in 1859, the results of 

 some experiments in which he was engaged, on continuous 

 brakes for arresting the motion of railway trains.f The 

 brakes were applied when the train was running on a 

 level line at different velocities, with the average results 

 estimated as follows : — 



20 miles per hour 24 yards. 



30 „ „ 53 » 



40 ,. „ 94 » 



50 „ „ 147 ,, 



60 „ „ 212 „ 



From this Table it will be seen that the distances the train 

 ran after the brakes were applied were as the square of 

 the velocities. 



The brief account here given of the contributions to 

 this historic controversy by members of this Society 

 would hardly be complete if I omitted the review of 

 Ewart's paper by Eaton Hodgkinson, F.R.S., published 

 in Vol. XII. of the Memoirs, an abstract of which also 

 appears in Dr. Angus Smith's Centenary of Science in 

 Manchester.^ 



' Manchester Memoirs, Vol. XXXVI., p. 5. 



+ Proc. Manchester Lit. and Phil. Soc, Vol. I., p. 178. 



X Manchester Memoirs, Vol. XXIX., pp. 253-256. 



