56 THE POPULAR SCIENCE MONTHLY. 



We now proceed to the measurements and records that are more 

 especially the subject of this memoir. 



Energy may be defined as the length of time during which a per- 

 son is wont to work at full stretch, day by day, without harm to him- 

 self, in obedience to an instinctive craving for work, and endurance 

 may be tested by the same observation if an adequate motive for work 

 be supplied. Some persons seem almost indefatigable ; they are never 

 happy or well except when in constant action ; and they fidget, fret, 

 and worry themselves under enforced idleness. Others, whose vitality 

 is low, break down under a small amount of strain, and their happiness 

 lies mainly in repose. The true tests would undoubtedly be physio- 

 logical, and of considerable delicacy, but they have yet to be dis- 

 covered, or at least to be systematized for anthropometric purposes. 

 They would measure the excess of waste over repair consequent upon 

 any given effort, and would furnish the indications of a loss of capital' 

 which, if persevered in, must, infallibly lead to vital bankruptcy. Now, 

 when a haberdasher examines a piece of cloth to learn its strength, he 

 handles and pulls it gently in different directions, but he does not care 

 to tear it to pieces or to strain it. He learns by the way it behaves 

 under a moderate tension how it would support a great deal more of 

 it. So it may prove to be with physiological tests, as applied to the 

 determination of the amount of endurance. The balance of the living 

 system might be artificially disturbed by a definite small force, and its 

 stability under the influence of greater forces might thereby be in- 

 ferred. Unfortunately, the only convenient tests of a person's endur- 

 ance that are now available are records of such feats of sustained 

 bodily or mental work as he may have recently performed, that were 

 not succeeded next day by feverish excitement or by fatigue, but 

 whose effects were entirely dissipated by a single night's rest. 



The faculties about which I have next to speak admit of being 

 developed in a high degree by exercise, and some difficulty will always 

 arise in knowing how far their development may be due to nature and 

 how far to practice. This difficulty is, however, of less importance 

 than it might appear to be. All our faculties are somewhat exercised 

 in the ordinary course of life, and when we begin to practice any 

 special test, though our skill increases rather quickly at first, its rate 

 of progress soon materially lessens, and we are able to judge with 

 sufficient precision of the highest point which we can hope to attain. 

 When recording the results of any test it would be sufficient to append 

 a brief note concerning the amount of previous practice. 



The strength is best measured by a spring dynamometer, of which 

 the frame-work is held in the left hand with the arm extended, while 

 the spring is drawn back by the right hand in the attitude of an 

 archer. This is the test used by the Anthropometric Committee ; it 

 only refers to the strength of the arms, but that is in most cases 

 sufficient to express the general muscular power, and it has the ad- 



