MENTAL DISCIPLINE IN EDUCATION. 699 



of solid bodies must, therefore, be.much denser than those of gases, and 

 exert also a more intense effect on the nerves of our eyes, " Light- 

 conductors " differ, therefore, from " light-radiators " by the lesser 

 density of their waves of light ; for which reason they cannot, under 

 ordinary circumstances, form " optical molecules," as I expressed on 

 another occasion. How powerfully the condensation of the waves of 

 light affects the eye is shown by the effect of collecting lenses. 



The minimum of density which a body must possess to become 

 light-radiating that is, to become self-luminous to the eye, or to ap- 

 pear a source of light is just now not known; but one sees, if this 

 view is correct, the possibility of even vapors or dense gases becom- 

 ing luminous, as Frankland tried to prove. The results of his experi- 

 ments might even serve as foundation for the lowest limit of density, 

 if it were not so very difficult, nay, even just now impossible, to make 

 such an experiment in a manner so as to exclude every doubt about 

 the assisting influence of solid bodies. English Mechanic. 



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MENTAL DISCIPLINE IN EDUCATION. 



By a. G. MEEWIN. 



I THINK it is safe to assume, on the one hand, that all, or nearly 

 all, mental discipline is of value ; and, on the other, that all, or 

 nearly all, knowledge is of value. It will also be conceded that a life 

 spent in disciplining the mind, while the mind so disciplined is never 

 employed in the direction of utility, is a life wasted. It seems equally 

 true that utility, when so narrowed as to relate only to the outward 

 trappings of the human being, is not real utility. 



By mental discipline we mean nothing more than habit of men- 

 tal action. The disciplined mind does not differ in kind from the un- 

 disciplined any more than the strength of a man differs in kind from 

 the strength of a child. It is evident that the best mental discipline 

 must be that which prepares the mind to grasp and direct the facts, 

 realities, and influences, on which human well-being depends. 



It is thought that there is study which gives mental power or dis- 

 cipline, while it results in little useful knowledge. By a method of 

 study the mind is to be developed into an intellectual Samson, but a 

 blind Samson ; and it is hoped and believed that a mind so trained 

 will do something better than to involve itself and others in a com- 

 mon ruin. That is, it is assumed that a habit of thought which does 

 not lead to useful knowledge in school, is tlie habit of thought which 

 will lead to useful knowledge in common affairs of life. 



The study of a dead language is supposed to give this mental dis- 

 cipline. Such study has almost nothing to do with present realities. 



