258 DISCOVERY CH. 



plant of a large works, or to apply it to the needs of 

 ordinary life, require aptitudes not commonly possessed 

 by the scientific investigator. The engineer usually 

 has such practical purposes in mind ; discoveries are 

 to him things to be used and not ends in themselves, 

 as they are to the man of science. He seeks not so 

 much to know Nature as to circumvent her ; and the 

 research which he undertakes or organises has for its 

 object the artificial preparation of substances which 

 are naturally rare, the production of a new process or 

 the improvement of an old, the design of machines 

 which will increase his power over her, and of instruments 

 which will enable him to laugh at limitations of time 

 and space. 



Research is necessary for these advances, but the 

 spirit in which it is carried on is essentially different 

 from that of the scientific worker. The engineer or the 

 inventor first of all perceives a need and then endeavours 

 to devise a means of meeting it. If he is of a scientific 

 type of mind he will make an accurate analysis of the 

 conditions to be fulfilled, and then design his machine 

 or instrument to fulfil them ; but the usual way is to 

 find practically what will perform the required functions, 

 and to leave experience or scientific knowledge to 

 indicate how improvements may be effected. 



The two methods may be illustrated by the discovery 

 of the safety-lamp for miners. With no access to 

 scientific works, or intercourse with scientific men, 

 George Stephenson constructed a safety-lamp which, 

 like Davy's, depended upon the principle that the flame 

 would not pass through tubes of small diameter and 

 ignite explosive gases outside. Stephenson first made 

 a lamp with a long chimney and a tube at the bottom 

 to admit air for the flame. As this was found to give 



