154 ANNUAL OF SCIENTIFIC DISCOVERY. 



CHLORIDE OF SILVER PILE. 



This pilo, inclosod in a rubber-box hcrmeticalh^ closed, can 

 advantageously replace the bulky apparatus called continuous 

 currents, which are ordinarily employed in medical practice. A 

 battery of 42 couples of chloride of silver correspond, in electro- 

 motive force and intensity, to 84 of the sulphate of copper couples 

 of llemack, and to the volume and weight of one only of these 

 last. 



It can render ^reat service in inflaming mines, torpedoes, etc. 

 Attached to a bobbin of Kuhmkorff it can serve in the case of in- 

 llanunations; it can also replace (he electrophorus of chemical 

 laboratories. Its use is indicated on the electric telegraph in sig- 

 nalizing an accident, or in notifying of danger. — Compics Eendus^ 

 May 3, 18G9. 



VELOCITY OF ELECTRIC CURRENTS. 



At the meeting of the American Association at Salem, Prof. G. 

 W. Hough, director of the Dudley Observatory, read a paper 

 *'0n the Velocity of the Electric Current over Telegraph Wires." 



He stated that the law of apparent velocity was directly pro- 

 portional to the magnetic force of the current. This was shown 

 to be the fact from a large number of experiments made over 

 lines of different lengths. He also stated that the real velocity 

 of the wave had never been measured, but the velocity obsei*ved 

 was due to the diflerence of mechanical cift^cts produced by the 

 current when the line was opened at alternate ends. 



ELECTRIC SPARK FIGURES. 



Mr. E. W. Blake, Jr., described a new method of his own dis- 

 covery, of producing by the electric spark figures similar to those 

 of Leichtenberg. -Warming a plate of tin or mica upon w^hich 

 pitch had been allowed to fall up to the softening point of the 

 pitch, the communication of the electric spark produces a star- 

 shaped figure from positive electricity, and circles from negative 

 electricity. Leichtenberg's process prepares the pitch b}' covering 

 it with some fine powder. No impression is produced upon cold 

 pitch. Resin and sealing-wax give good impressions, but the 

 best come from common pitch or Burgundy pitch. It is essential 

 that the under side of the plate be held to the flame. — Meeting of 

 the Am. Ass. 



NON-EXISTENCE OF THE ELECTRIC FLUID. BY PROF. VANDER 



WEYDE, M.D. 



In tlie same manner that the investigations and discoveries of 

 20 years ago have proved that the so-callc*! caloric fluid has no 

 existence, and that heat is only a state of matter, — a mode of 



