302 Mr. James Wimshurst [April 27, 



of this, I may mention that Professor Sylvanus P. Thompson at once 

 placed all his literature and even his private notes of reference at my 

 service. 



I will now endeavour to point out the more prominent features of 

 the influence machines which I have present, and, in doing so, I must 

 ask a moment's leave from the subject of my lecture to show you a 

 small machine made by that eminent worker, Faraday, which, apart 

 from its value as his handiwork, so closely brings us face to face with 

 the imperfect apparatus with which he and others of his day miide 

 their valuable researches. 



The next machine which I take is a Holtz. It has one plate 

 revolving, the second plate being fixed. The fixed plate, as you see, 

 is so much cut away, that it is very liable to breakage. PajDer in- 

 ductors are fixed upon the back of it, while opj)osite the inductors, 

 and in front of the revolving plate, are combs. To work the machine 

 (1) a sj)®cially dry atmosphere is required ; (2) an initial charge is 

 necessary ; (3) when at work the amount of electricity passing 

 through the terminals is great ; (4) the direction of the current is 

 apt to reverse ; (5) when the terminals are opened beyond the 

 sparking distance the excitement rapidly dies away ; (6) it does not 

 part with free electricity from either of the terminals singly. 



It has no metal on the revolving jjlates, nor any metal contacts ; 

 the electricity is collected by combs which take the place of brushes, 

 and it is the break in the connection of this circuit wliich supplies a 

 current for external use. On this point I cannot do better than quote 

 an extract from page 339 of Sir William Thomson's Paj^ers on 

 Electrostatics and Magnetism, which runs : " Holtz's now celebrated 

 electric machine, which is closely analogous in jDrinciple to Varley's 

 of 1860, is, I believe, a descendant of Nicholson's. Its great power 

 depends uj^on the abolition by Holtz of metallic carriers and metallic 

 make-and-break contacts. It difl'crs from Varley's and mine by 

 leaving the inductors to themselves, and using the current in the 

 connecting arc." 



In respect to the second form of Holtz machine (Fig. 4) I have 

 very little information, for since it was brought to my notice nearly 

 six years ago I have not been able to find either one of the machines 

 or any person who had seen one. As ^\ill be seen by the diagram it 

 has two discs revolving in opposite directions, it has no metal sectors 

 and no metal contacts. The " connecting arc circuit " is used for the 

 terminal circuit. Altogether I can very well understand and fully 

 appreciate the statement made by Professor Holtz in ' TJiJiwuiborn' s 

 JonrnaV of May 1881, wherein he writes "that for the purj^ose of 

 demonstration I would rather be without such machines." 



The first type of Holtz machine has now in many instances been 

 made up in multiple form, within suitably constructed glass cases, 

 but when so made up great difficulty has been found in keeping each 

 of the many plates to a like excitement. When difierently excited 

 the one set of plates furnished positive electricity to the comb, while 



