436 A. M. Mayer— Method of investigating the 
idocrase is especially interesting; for while we find these 
minerals frequently associated, we have nowhere else found 
the crystals of the two penetrating and interlacing each other, 
so as to form between them a uniform mass, yet each mineral 
retaining its identity. 
t can be readily understood how two such minerals as lime, 
garnet and idocrase may occur in the manner just mentioned, 
when we consider the formule of the two: 
arnet, (48°+38)*Si9 
Idocrase, ($R°+-28)? Si3. 
ART. —On a new method of investigating the Composite 
Nature of the Electric Discharge ; by ALFRED M MAYER. 
rmed Henry’s discovery, on examining the nature of the 
discharge by means of a revolving mirror. Subsequently 
Rood (in a series of classical researches, published in this 
Journal in 1869-71-72) studied the multiple character of the _ 
discharge of the inductorium by means of rotating dises perfor- 
ated with narrow radial slits. In 1873 Cazint also investigated 
the discharge with the rotating disc. The method I have de- 
vised leads us directly, by the simplest means, to phenomena 
which cannot be revealed by either revolving mirror or rotating 
disc. The first method that occurred to me was to attach a- 
delicate metallic point to a vibrati tuning-fork, and to send 
the discharge from this point, through lamp-blackened paper, to 
a revolving metallic cylinder, on which the paper was stretc 
We can to some extent analyze the electric discharge, in these 
conditions, from the series of perforations left in the paper 
in the trail of the vibrating fork. This method, though beauti- 
ful as an illustration, is useless as a means of investigation ; 
_ for the metal cylinder, the paper and the fork form a species 
Leyden jar, which is always in the circuit of the particular 
~ disch whose nature you would investigate. The above 
method, though original with me, cannot be claimed as MY 
| Weber die cletische Paschenentadung isp. 192 
Jenteal Os Pippen sel pete Pogg. Ann., vol. cxvi, p- 
