Intelligence and Miscellaneous Articles. 403 



3. The conductor must have such dimensions that the flow is 

 considerable. 



4. Before commencing each experiment, the tension of the appa- 

 ratus must be kept constant for some time, in order that the con- 

 ducting wire may attain a permanent state. 



Variation of the tension in different parts of the conductor. — The 

 tension of the string, which at one end is connected with the 

 electroscope, and at the other with the ground, has half the tension 

 of the source. It has been found, moreover, that, by employing 

 the method of discharges, the dynamic charge of a string, that is to 

 say, the quantity of electricity with which it is charged while the 

 discharge takes place, is half the static charge, or the charge which 

 it has while in connexion with the source of electricity not insulated 

 from the ground. 



The laws of derived currents have been verified by the same 

 method, by connecting the electroscope with the ground by several 

 strings simultaneously, and by forked strings. 



The intensity of the flow is proportional to the tension of the source, 

 if the extremity of the string is in contact with the ground. — The 

 gold-leaf electroscope was graduated so as to determine two tensions, 

 which were in the ratio of 1 to 2 ; and the method of discharges 

 showed that the intensity of the flow was perceptibly in the same 

 ratio. 



The intensity of the flow is proportional to the section of the con- 

 ductor. — A first series of experiments showed that the flow did not 

 vary, when the section of the conductor was constant, even when 

 the surface varied. With cotton threads, whether insulated or 

 bound together, the intensity of the flow was not modified. The 

 same result was obtained with a silk ribbon, which was successively 

 folded so as to form a plain surface, rolled several times on itself, 

 and lastly rolled once so as to form a cylindrical sac. 



A second series of experiments was made by using columns of oil 

 of different lengths and sections, and measuring each time the corre- 

 sponding flows. 



On the dynamic charge. — The meaning of this term has been 

 explained, and it has been seen that it is double the statical charge. 

 This result agrees with Ohm's law on the distribution of tensions 

 on the course of a conductor, and shows at the same time that the 

 dynamic charge, like the statical, is distributed on the surface of 

 the conductor. The author has endeavoured to confirm this principle 

 by other experiments, showing that the dynamic discharge depends 

 on the surface of the conductor, and not, as with the flow, on the 

 section solely. Thus the dynamic discharge of ten insulated cotton 

 threads bears to these threads united in a bundle the ratio 2 to 1 . 

 Analogous results have been obtained by using silk ribbons in 

 different shapes. — Annates de Chimie et de Physique, vol. lix. p. 5 ; 

 Bibliotheque Universelle for June 1860, p. 146. 



wood's fusible metal. 

 Dr. B. Wood, of Nashville, U.S., has secured a patent for an alloy 

 composed of cadmium, tin, lead and bismuth, which fuses at a tem- 

 perature between 150° and 1 60° F. The constituents of this fusible 



