188 



Anniversary Meeting. 



[Noy. 30, 



scale the cost of which would be quite prohibitory if it were a matter 

 of science pure and simple. Take for example the experiments made 

 by Faraday on 100 miles of submerged covered wire at the Works of 

 the Electric Telegraph Company. 



When we think of the progress of science, both abstract and applied, 

 during the last half-century, we can hardly help speculating as to the 

 possible increase of scientific knowledge half a century heuce. Per- 

 haps we might be tempted to think that the mine must have been so 

 far worked that no great quantity of precious ore can still be left, 

 except what lies too deep for human power to extract. Yet surely 

 the progress of knowledge in the past warns us against any hasty 

 conclusion of the kind. How often have accessions to our knowledge 

 been made which were quite unforeseen and quite unexpected, and 

 how can we say what great discovery may not be made at any 

 moment, and what a flood of light may not result from it ? 



In what direction such discoveries may be made, it would be rash 

 indeed to attempt to predict. Tet one cannot help thinking of one or 

 two cases in which we seem almost in touch of what if we could reach 

 it would probably give us an insight into the processes of nature of 

 which we have little idea at present. Take for example the theory of 

 electricity as contrasted with the theory of light. In the latter we have 

 the laws of reflection and refraction, which have long been known, the 

 remarkable phenomenon of interference, the curious appearances which 

 we designate by phenomena of diffraction. But all these fall in the most 

 simple and natural way into their places when we have arrived at the 

 answer to the question, What is light ? which is furnished by the state- 

 ment, — Light consists in the undulations of an elastic medium. But we 

 are not at present able to give a similar answer to the question, What 

 is electricity? The appropriate idea has yet to be found. We know 

 a great deal about its laws, and its connexion with magnetism and 

 chemical action ; we are able to measure accurately physical constants 

 relating to it ; we make it subservient to the wants of daily life ; and 

 yet we are unable to answer the question, What is it ? Could we 

 only give a definite answer to this question, it seems likely that the 

 production of electricity by friction, electrostatic attractions and 

 repulsions, the laws of electrodynamics, those of thermodynamics, the 

 nature of magnetism, and magneto-electric phenomena would prove to 

 be all simple deductions from the one fundamental idea. Nay more : 

 so closely is electricity related to chemical action, that could we only 

 clearly apprehend the nature of electricity, it seems not unlikely 

 that an unexpected flood of light might be shed on chemical com- 

 bination. 



Let me refer to one other instance in which a large accession to our 

 present knowledge seems not altogether hopeless. We know that 

 when an electric discharge is passed through a given gas, or between 



