g]g COMPAIUTIVE POWERS OF ELECTRICAL MACHINES, 



9 XII. 



Experiments on the comparative Powers of Cylinder and 

 Plate electrical Machines, and on a means of doubling* 

 trebling, or quadrupling their charging Power : by Mr. 

 John Cuthbertson and Mt\ G. J. Singer. Com- 

 municated by Mr. Singer. 



JL HE opinion of electricians has been at various times 



Best sliape for much divided with regard to the best form of an electrical 



electrical ma- raac hi ae ^ Globes, spheroid*, cylinders, and plates, have 



chine? doubt- 7 r , i •' • 



ed. been alternately employed and recommended by various 



experimenters: but the last two forms have been recently 

 hy far the most prevalent. The earlier electricians pro- 

 Formerlr but duced but slight electrical effects; and though some at- 

 ■hght effects tempts were made at improvement, by alterations in the 

 structure of the apparatus, ond by the adoption of ma- 

 chinery ; the tests of electrical action at that time known 

 were far from adequate to any accurate comparison of their 

 relative merits. The much improved construction of the 

 Improre- cylinder machine by Mr. Nairne, the experiments on elec- 



pwats. trical excitation by Mr. Nicholson, and the structure of 



the unrivalled Harlem apparatus by Mr. Cuthbertson, are 

 the circumstances that have most enlightened this subject; 

 and it is from these sources, the various opinions, that 

 have been entertained in this respect, have principally ori- 

 ginated. 



The influence of the hygrometrical state of the atmos- 

 __ . - phere on electrical experiments, and the considerable di- 

 eBced by slight versity of effect produced by slight alterations in the dis<? 

 circumstances. p 0s iti n f the apparatus, will convince every electrician, 

 that no just comparison of the merits of any two instru- 

 ments can be nu.de, unless they are employed in one situa* 

 tion, at the same time, and under similar circumstances. 

 These at- These essential requisites to just observation have been at- 

 tended to in tended to as strictly as possible in the following experi- 

 the following Vi. t ,,' v . r w • 



experiments, meats, made with the express intention or obtaining every 



useful information on this particular subject. 

 Instruments The instruments employed for comparison were a cylin- 



firo^ioyed. j er Q f j^ inc h es diameter (with a multiplying wheel and 



pulley, 



