﻿Mr. H. Wilde on a Property of the Magneto- electric Current. 55 



One method of mitigating this evil was to construct the ma- 

 chine of smaller dimensions,, so as to afford greater facilities for 

 the dissipation of the heat by radiation and conduction. But 

 even in the smaller machines an inconvenient residuum of heat 

 still remained when the machines were worked continuously for 

 a considerable time, such as to render it desirable to adopt some 

 means for abstracting the heat more rapidly. By means of a 

 current of water circulating in the hollow brass segments which 

 form part of the magnet-cylinder, Mr. Charles E. Ryder, the skil- 

 ful manager at the works of Messrs. Elkington and Co., has 

 happily succeeded in so far reducing this heating as to permit 

 of the machines being worked for days and nights together with- 

 out intermission, and without any sensible diminution of the 

 power of the current. 



The machines which have been found to be the most efficient 

 and economical in their working are those which have armatures 

 from 3 \ to 4 inches in diameter. The armatures are driven at 

 about 2000 revolutions per minute ; and the water, after having 

 passed through the magnet-cylinder, is used for supplying the 

 boilers which furnish the power for driving the machines. 



I have already shown elsewhere that the current from a small 

 magneto-electric or electromagnetic machine is sufficient to ex- 

 cite the great electromagnet of the 10-inch machine ; and it has 

 been further found, by my friend Mr. G. C. Lowe, that the cur- 

 rent from one small machine is sufficient to excite simultaneously 

 the electromagnets of several small machines. In a number of 

 3J-inch machines which have been constructed under my direc- 

 tion for Messrs. Elkington and Co., for the electrodeposition of 

 copper on a large scale, the currents from two 3J-inch electro- 

 magnetic machines are made to excite the electromagnets of 

 twenty similar-sized machines to a degree sufficient to bring out 

 the maximum dynamic effect of each machine. The electromag- 

 nets of the two 3 J-inch exciting machines are charged by the 

 current from a small 2^-inch magneto-electric machine ; but I 

 have found that nearly as good a result may be obtained from 

 the twenty machines by dispensing with the small magneto- 

 electric machine, and employing the residual magnetism of the 

 two 3J-inch exciting machines in a manner similar to that de- 

 scribed, almost simultaneously, by Mr. Farmer*, Messrs. Var- 

 leytj Mr. Siemens %, and Sir Charles Wheatstone §. 



* Letter to the Author, November 9, 1866, Salem, Mass. U.S., Pro- 

 ceedings of the Literary and Philosophical Society of Manchester, Febru- 

 ary 19, 1867. 



t Specification filed at the Office of the Commissioner of Patents, De- 

 cember 24, 1866. 



X Specification filed at the Office of the Commissioner of Patents, Janu- 

 ary 31, 1867. 



§ Proceedings of the Royal Society, February 14, 1867. 



