REPOUT 



OF 



RECENT PROGRESS IN PHYSIOS.. 



BY Dr. JOH. MULLER, 



PROFESSOR OF PHYSICS AND TECHNOLOGY IN THE UNIVERSITY OF FREIBURG. 



[Translated from tiie German for the Smithsonian Institution.] 



This work, which was commenced in the last annual report, p. 311, 

 is continued in the present volume. 



Some of the subjects discussed may be familiar to the readers ot 

 English scientific works, but these are retained for two reasons— firstly, 

 because their omission would destroy the continuity of the narrative of 

 scientific progress, and, secondly, because these very subjects serve 

 as a text for the introduction of views held by continental philoso- 

 phers, with very few exceptions, and yet not sufficiently well known 

 to those who derive their information from the ordinary English 

 works upon electricity. 



SECTION FIRST. 



FRICTIONAL ELECTRICITY. 



ELECTRIC RELATIONS OF DIFFERENT SUBSTANCES, ELECTRICAL MACHINES, AND 



ELECTROMETERS. 



§ I. Electricity of machine-made paper. — It has been long known 

 that paper becomes electrified by friction ; and the excitation of elec- 

 tricity in the manufacture of machine paper is not a new phenomenon ; 

 possibly there were few proprietors of paper mills who had not observed 

 it, yet this phenomenon was described for the first time by Eaukel. — 



(Pogg.Ann.,L\^,477,) i • ,1.. 



In every machine the paper becomes highly negative on leaving the 

 last pair of pressing rollers. If the finger is brought near to the 

 paper, between the finishing rollers and the reel, a brush passes from 

 it to the paper, and a Leyden jar can be readily charged. The paper, 

 too, which has been wound upon the reel is electrified, and notably so 

 when there is a large roll upon the reel. When the paper is cut off 

 from the reel, and the long sheets are pulled apart, very strong, 

 brilliant sparks pass between them. 



This electricity evidently arises merely from the heating of the 

 paper and its compression by the rollers. No rubbing friction can 

 take place since the velocity of revolution of all of the rollers is ex- 

 actly the same. 



