206 



Capt. M. Greenwood. 



0*5 ampere load their professional subject had an efficiency of between 15 

 and 18 per cent, (revolation rate between 67 and 72), which rose to 24 per 

 cent, when the load was furnished by a I'o ampere current. The reader 

 might infer that the muscular efficiency improved with load. This, however, 

 is a mere consequence of the method of calculation. Table VII gives the 

 observations, and it will be seen that for this range the linear equation 

 H = aW + c very fairly represents the data. Adopting the above definition, 

 the efficiency is l/a, in the particular case, 0*2993. Now Benedict and 

 Cathcart's subject's net efficiency is W/(a'W + c — 1-17) and his gross efficiency 

 W/(«W + c), which obviously increase with W and will only reach the value 

 l/a when W is infinite. In effect, using the formula we have, for the 

 particular values 0'48 cal. and 1'57 caL, "net efficiencies " 0"17 and 0'24 ; for 

 "gross efficiencies," 0*12 and 0'21, which agree, to this number of decimals, 

 with the observed means. 



Table VII. — Heat Production and Work. Observations of Benedict and 

 Cathcart on M. A. M. pedalling at the rate of 68-72 revolutions per 

 minute (inclusive). 





Observed heat production. 



Mean of 

 observations. 



Heat production given by 



Work done. 



formula 

 Heat = 3-3415 Work +.2-4131. 



calories. 



calories. 







0-47 



4-01, 4-01 



4-01 



3-98 



0-48 



3 -86, 3 -88, 3-83, 4-13, 3 -90 



3-93 



4-02 



0-49 



4-1.5, 3-94 

 6-73 



4-05 



4-05 



1-19 



6-73 



6-39 



1-20 



6-65, 6-81 



6-73 



6-42 



1-33 



6-95 



6-95 



6-86 



1 -35 



6 -.97 



6-97 



6-92 



1 -36 



7-08 



7-08 



6-96 



1 -56 



7 '44 7 '66 

 7-87, 7-59, 7-53, 7-64, 7-41, 

 7 -51, 7 -55 



7-55 



7-62 



1 -57 



7-59 



7-66 



1-59 



7-56 



7-56 



7-73 



Hence the data are quite consistent with a constant efficiency as just 

 defined for all loads within the observed range. A fortiori, Amar's base line 

 is highly objectionable, and no doubt over-estimates the real efficiency of the 

 machine. A labourer who rests on Sunday and does eight hours' work on 

 Monday really performs some muscular work, although not industrial work, 

 on Sunday ; the Monday's work is not a mere addition to that of Sunday, but, 

 in part, a substitution of purposeful for aimless activity. Hence to deduct 



