M. Scheerer on the Products of Oxidized Pyrites, 265 
in the adjoining conductor; since this tends to produce a 
current in the opposite direction. 
96. It would also appear from the perfect neutralization 
which ensues in the arrangement of the last paragraph, that 
the induced current in the adjoining conductor is more power- 
ful than that of the first conductor; and we can easily see 
how this may be. The two ends of the second coil are joined, 
and it thus forms a perfect metallic circuit; while the circuit 
of the other coil may be considered as partially interrupted, 
since to render the spark visible the electricity must be pro- 
jected, as it were, through a small distance of air. 
97. We would also infer that two contiguous secondary 
currents, produced by the same induction, would partially 
counteract each other. Moving in the same direction, they 
would each tend to induce a current in the other of an op- 
posite direction. This is illustrated by the following ex- 
periment: helix No. 1 and 2 were placed together, but not 
united, above coil No. ], so that they each might receive the 
induction ; the larger was then gradually removed to a greater 
distance from the coil, until the intensity of the shock from 
each was about the same. When the ends of the two were 
united, so that the shock would pass through the body from 
the two together, the effect was apparently less than with one 
helix alone. The result, however, was not as satisfactory as 
in the case of the other experiments ; a slight difference in 
the intensity of two shocks could not be appreciated with 
perfect certainty. 
[To be continued.] 
XLVIL On the Natural Products which originate from the ac-‘ 
tion of the Atmosphere on Iron Pyrites, Th, Scheerer^. 
TT is a well-known fact, that iron pyrites, in the finely divided 
state in which it occurs in alum slates, is easily oxidized by 
the atmosphere, causing the parts exposed to acquire a reddish 
brown colour ; nevertheless, the products of this decomposi- 
tion are seldom to be found, from the rain washing them away. 
In a spot near Modum in Norway, I met with a cavity in the 
mountains where they were deposited as incrustations, safe 
from all destructive influences. Three distinct layers were 
evident. 
The first and upper layer is a dark brown massive mineral 
with which the slate is impregnated : A. 
An extract obligingly communicated by the author from the original 
paper published in Poggendorff’s Annalen, vol. xlv. p. 188. 
