KNOWLEDGE AND OPINION. ft? 



as soon as he tries to put his belief into practice, 

 and sets out to look for London in Normal d y or 

 in Provence, he will very quickly discover his 

 blunder, and fnid himself pulled up short at last 

 by the stern logic of facts. 



And this leads us on to the real test and justifi- 

 cation of all scientific belief — its constant verifi- 

 cation in the realities of life. An eclipse of the 

 sun, a transit of Venus, a comet's return, is pre- 

 dicted confidently for such and such a day and 

 hour. The day and the hour arrive, and there, 

 punctually to the minute, the sun is eclipsed, the 

 transit is observed, the comet returns. It is just 

 the same in all other things. What is the justifi- 

 cation of our science of physics ? Why, the fact 

 that in accordance with its laws we make steam- 

 engines which do go, we construct microscopes 

 which do magnify, we produce bridges and rail- 

 roads and ships which do perform the work we 

 expect of them I What is the justification of our 

 electrical science ? Why, the existence of tele- 

 graphs, telephones, electric lights, electro-plate 

 spoons, and the thousand other practical outcomes 

 of our knowledge of electiicity ! What is the 

 justification of our chemical science? Why, the 

 fact that we can make dynamite which will blast 

 the most solid rocks, chloroform wliich will still 

 the most poignant pain, gas which will lighten the 

 darkest night, acids which will dissolve the 



