127 



successfully attained for some time by one means, and it is proposed 

 to attain it more advantageously by a newly-discovered means. 

 Very often the mere acquisition of knowledge suggests some useful 

 purpose to which it may be applied. To improve upon Shake" 

 speare, not in poetry, but in sentiment, — 



" How oft the sight of means to do good deeds, 

 Makes good deeds done." 



The knowledge of the motive power of steam, the knowledge that 

 electricity can be transmitted through a long wire and act upon a 

 magnetic needle at the end of it, and the knowledge of the inflam- 

 mable properties of coal gas, are three most apposite, and altogether 

 most extraordinary illustrations of this. In all the three cases it was 

 in men's minds for a long time to apply the knowledge to the 

 useful purposes of life, and each practical application in succession, 

 as Mr. Kendall has already remarked with reference to the steam- 

 engine and its off-shoots, existed for years in the state of theory ; 

 that is, though there was no doubt about the knowledge, as 

 knowledge, there was a doubt whether, when applied to practical 

 purposes, it would produce the desired ends. I need not say how 

 fully all these ends have been realised. 



The second aspect of theory and practice is that in which 

 there is an urgent need for something — some end is very desirable, 

 and men are prompted to search for the means. Now, which kind 

 of men would most likely be successful in the search ? The self- 

 styled practical men, those mere mechanics, who just work by the 

 light of a candle, which some have made and others have lighted 

 for them, or rather men of high intellectual attainments in the 

 subject matter, in other words — those who have a rich store of 

 theoretical knowledge to draw upon ? In the case of the former, 

 the result would very probably be like Mr. Kendall's siphons and 

 pit cages ; with the latter, every condition, positive and negative, 

 would be thoroughly investigated, and if the end were attainable 

 at all in the state of knowledge at the time, the means would be 

 brought to light. About sixty years ago there was a very pressing 

 need for some contrivance to prevent the fearful loss of life by the 

 explosions of fire damp, and practice showed its good sense by 



