756 POPULAR SCIENCE MONTHLY. 



in borrasca, and they may never again pay a profit to their 

 owners. Still, with faith and endurance that are sublime, the 

 heroes of the Comstock cling to its fallen fortunes, and continue 

 the search for new bonanzas. 



[Editorial Note. — The full story of the mines, as illustrated by the great Comstock 

 lode, prepared by Mr. Shinn, will constitute the next volume of the Stoi'y of the West Series, 

 edited by Mr. Ripley Hitchcock, to be published by D. Appleton & Co. in October. Our 

 readers need hardly be told that Mr Shinn has special qualifications in his familiar acquaint- 

 ance with the subject and his rare literary skill, which will impart special interest and value 

 to this work ] 



A MEASURE OF MENTAL CAPACITY. 



By Dk. EMIL KRAEPELIN, 



PROFESSOR OF PSYCHIATRY AT HEIDELBERG. 



(From, an Address delivered in behalf of the Heidelberc/er Frauenverein.) 



WE are able to calculate almost precisely the amount of work 

 any given machine — as a steam engine or an electric-light- 

 ing plant — is capable of performing, and the amount of fuel that 

 will be required to develop the calculated power. When we 

 come to man we are much less certain, although a skillful army 

 surgeon can tell almost at a glance whether the recruit standing 

 before him is strong enough to meet the requirements of the 

 service, and there are machines in the market that will inform 

 us in what time we can pull a given weight to a given height. 

 But we have no measure that we can apply to the capacity for 

 mental work, and no units of mental valuation. The most we 

 can do is to compare the intellectual capacity of one man with 

 that of another by the mental results they have severally achieved 

 in practice. When we wish to test the fitness of a candidate for 

 a position of trust or responsibility, we subject him to an exami- 

 nation, which relates, however, mostly to what he has learned, 

 and from which we guess in a rather indirect way what he may 

 be capable of doing in the future, and with relation to other 

 matters than those on which we examine him ; and the test is very 

 often deceptive : for those who have made the most brilliant 

 displays in the examination frequently fail in capacity to make 

 practical application of what they have learned only theoretic- 

 ally ; or they fail by irregularity, frequent and marked changes 

 in their disposition to work, want of endurance, or too great de- 

 pendence on external conditions, of which the examination gives 

 no prediction. Such efforts as have been made to obviate this 

 diSiculty have hitherto failed to meet their object. 



It has, however, recently become possible to reach fairly ap- 

 proximate conclusions concerning mental capacity, such as other- 



