lxxii GENERAL SUMMARY OF SCIENTIFIC AND 



ELECTRICITY. 



Edlund has published a complete paper on the nature of 

 electricity, in which he maintains with great ability the the- 

 ory that electricity is identical with the luminiferous ether, 

 and in which lie deduces most, if not all, electrical phenom- 

 ena from this supposition. 



Mixter has called attention to the remarkable increase in 

 length of the spark of the Iloltz machine by placing a mi- 

 nute gas jet between the balls affording the sparks. In this 

 way the spark, which before was less than ten inches, became 

 more than twelve, a brass ball having only a trifling influ- 

 ence of the same sort. 



Rosetti has investigated the action of the Holtz machine, 

 and finds that it follows the law T of Ohm completely, but that 

 the electro-motive force and the resistance are enormous. In 

 his instrument the electro-motive force was 57,000 volts when 

 the atmospheric moisture was 0.35, and the resistance, w T ith 

 two turns per second, 2,680,000,000 ohms. From his experi- 

 ments he deduced 428 as the mechanical equivalent of heat. 



Mr. W. Whitehorn has communicated to the Physical So- 

 ciety of London some experiments on the electric conductivity 

 of glass. He shows that, although a perfect non-conductor 

 at ordinary temperatures, yet glass, when heated to redness, 

 allows the electric current to pass freely. Even at the tem- 

 perature of boiling water a slight amount of electricity is 

 conve)'ed by it. The resistance at a temperature of 165 C. 

 is nearly forty times that observed at a temperature of 300. 

 The glass used by Mr. Whitehorn contained oxides of lead, 

 thereby making it a better insulator than other kinds of 

 glass. 



Lesueur recommends strongly the use of zinc to prevent 

 the formation of incrustations in steam-boilers. His attention 

 was called to the subject by observing that the brass stays 

 of a surface condenser in a steam-vessel were reduced, after 

 a few years of service, to a mass of spongy copper, the zinc 

 having entirely disappeared. This having occurred repeat- 

 edly, the constructors of these Condensers placed zinc in the 

 condensers, and observed that not only was the brass no 

 longer attacked, but the boilers supplied from these con- 

 densers were entirely free from incrustation. Direct exper- 



