162 Miscellaneous Intelligence. 
third the length of the spark when three pair of rubbers were on 
the machine. ; 
6inches. . .12inches. . . 18 inches. 
Tc pessetl diana cath adie ous na satin, Le 
ah. maptae a SAE dynamite v9 
SR er aA |: RE EERR Tele i+ <n 
De tees ol en Se te ag 
Bib. Univ. xxiv. 187. 
7. Improvement of the Leyden Jar.—M. Metzger has also varied 
the construction of Leyden jars, so as to augment their capa- 
city without increasing their apparent volume. For this purpose 
having two jars of proper dimensions, he simply places one within 
the other, so that they shall apply pretty correctly, and thus have a 
capacity of charge nearly proportional to, the whole surface of 
coating, without increasing the volume of the whole beyond that of 
the larger jar. Jars made slightly conical would answer well for 
this purpose.—Brb. Univ, 191. 
8. Electricity on Separation of Parls.—In the water-proof cloths 
manufactured by M. Mackintosh of Glasgow, where two pieces 
are cemented together by caoutchouc dissolved in coal tar oil, the 
adhesion is such that when the two are torn asunder in the dark, 
there is a bright flash of electric light, similar to that produced by 
separating plates of mica, by breaking Rupert’s drops, or by 
breaking barley-sugar, or sugar-candy. Upon trying this experi- 
ment with different substances, it was found that flashes of light 
were distinctly produced, by tearing quickly a piece of cotton 
cloth.—£din, Jour. x. 185. 
9. Electric Light —Having a metallic wire covered with silk, 
form it into a close flat spiral, taking care that the revolutions 
touch each other. Their number may be arbitrary, more than 
twenty-four have not been used. The properties of this spiral 
when it forms part of the voltaic circuit are well known, but pass 
through it a charge of common electricity, such as may be taken by 
two square feet of coated surface, moderately charged, and a vivid 
light, something resembling that of an artificial fire-work, will occur, 
originating from the centre of the spires. It may be seen very 
distinctly without darkening the chamber where the experiment is 
made. 
M. Leopold de Nobili, who describes this experiment, considers 
the phenomenon as perfectly new. If the wire be folded backwards 
and forwards, so as to form a rectangular surface, then the electric 
discharge only produces a faint light at each corner, and this he 
considers as the light produced by the escape of the electricity into 
