ELECTRICAL AXD MAGNETIC DISCOVERIES OF FARADAY 649 



moment of breaking circuit, the system must vanish, and we obtain the 

 energy stored up in this space surrounding the wire in the bright spark 

 known as the extra current. 



What a flood of light this throws on many experiments such as those 

 of Wheatstone, on the velocity of electricity. With his wire arranged 

 in parallel loops around an ordinary room, he discharged a Leyden jar 

 through it, and assumed that the electricity passed through the whole 

 wire before a spark could form at the distant end. But we know that 

 whole room was instantly filled with moving lines of magnetic force, 

 which induced currents in every wire they crossed, and hence what 

 Wheatstone measured was merely the current induced from one wire 

 or those near it. 



Thomson and Maxwell have shown that the medium around a wire 

 carrying an electric current is in motion, and that the vortex filaments 

 form Faraday's lines of magnetic force; for Faraday's discovery of the 

 magnetic rotation of the plane of polarization of light can be explained 

 in no other way. 



Thus the discoveries of Faraday have been engrafted on our science, 

 and form one of its most essential features. They are among the foun- 

 dation stones of the edifice of our science. 



We know far more than the electricians of that day, in the details of 

 the subject, and mathematics has given us a broad view of electricity 

 and magnetism, such as never before was obtained. In its practical use 

 and measurement we have made immense strides in devising methods 

 and instruments, and we now carry out our experiments on a scale which 

 Faraday could not attempt, seeing that subject, which has hitherto been 

 best adapted to the contemplation of a few philosophers, has become 

 of use to all, and electricity bids fair to become our most important 

 servant. 



The spark, which Faraday more than fifty years ago observed in a 

 darkened room, now blazes out almost with the power of the sun, but it 

 is still the spark of Faraday. Though it is a thousand times as large, it 

 is still made on the principles which Faraday laid down, and nothing 

 except mechanical details has ever been added to its process. 



How suitable, then, that we should remember his name on this 

 occasion, since his discoveries have served as the basis of all progress 

 in electrical engineering. Had Faraday not lived we should not have 

 been here to-night. True, as I have shown before, the progress of science 

 could only have been delayed by the absence of any one man, but how 

 long, in this case, we cannot tell. We can only receive with gratitude 



