Marts Mechanical Efficiency in Work Performance. 



409 



circumstances, any reason to hesitate before suggesting the possibility that 

 /, or (PV)5 p ' v , may finally be shown to have some definite relation to the 

 acceleration or sum of accelerations responsible for the quasi-pendular 

 movements from which the horizontal velocity is derived. 



As a summary to the sections dealing with mE', and with the velocity 

 factor, it may be stated, then, as not improbable that the empirical formula 

 0"426H = -J, <£(1/P) (PV) p,y , may finally be arranged in rational form in 

 some such manner as 



0-426H = imE'/. 

 Comlusion. 



Attention is drawn to the fact that there appears to be some definite 

 order in the heat productions dealt with as " cost of movement " when no 

 allowance is made for synchronous " cost of rest." The order developed 

 by dealing with the facts in this way is significant, in my opinion, of the 

 influence of that control exerted by the central nervous system in arranging 

 the phenomena of a moment to correspond with the requirements of that 

 moment. In my view " rest " is an entity, and not devoid of a dynamic 

 fraction, " movement " is again an entity of a different type, in which the 

 dynamic fraction is in the forefront, and on this view everything 

 occurring during movement is related to movement. In short, the view 

 is held that there is no " rest ' : in movement, and apparently with some 

 justification. It is also held, and apparently has indeed been shown, that the 

 cost of movement is identically the same whether the work performed by its 

 means is large or small. 



Attention is also drawn to the importance of an " economical rate " in 

 movement as the phenomenon of major interest, and as decided by relation- 

 ships to bodily dimensions of an exact kind. There is no sign, indeed, that 

 any other circumstances need be considered than mass and length in this 

 connection. 



Then, as to the " efficiency " prevalent in the performance of movement, 

 it would seem to vary inversely with the mass in motion, but the fact that 

 this is the case suggests at once the conception that this efficiency (so far 

 as it can be examined) is not a genuine efficiency, but is due to the 

 complication of a constant, perhaps, indeed, an absolute efficiency (100 per 

 cent.), by unknown internal resistance directly proportional to the mass 

 engaged in accomplishing visible external work again proportional to the 

 mass, so that the cost varies with the square of the mass. 



A similar point is even still more evident with regard to the " efficiency 

 of work performance." In this case a different mechanical problem, leverage 



VOL. LXXXIX. — B. 2 L 



