26 PAPERS, ETC. 
ference between the crystalline formation in the dark and 
that in the light. In the first, the crystals are decidedly 
larger, and longer, and more firm. In the last they have 
a more soluble appearance, and are not so firmly attached 
to the wire. Besides, the termination of the negative 
wire in the light is surrounded by a kind of halo of 
insulated specks of carbonate of lime, forming a small 
ball of about one-fourth of an inch in diameter. When 
viewed through a lens, it exhibits a singular disjointed 
appearance. Now the negative wire in the dark has had 
such an influence on that side of the glass jar, that it is 
being covered to a large extent by carbonate of lime for- 
mations, which is not the case with the similar wire in 
the light, save to a very limited extent. In fact, certain 
of the sun’s rays are electrical, and neutralize to a great 
degree, or materially change the electrical formation, which 
would take place were the experiment conducted in the 
dark. We have thus seen that the union of electrie action, 
with a moderately uniform temperature, and sufficieney of 
heat, to prevent congelation of the fluid under action, 
absence of light, together with the interposition of a more 
or less porous medium, will attract the crystallizable matter 
from its solution and produce a variety of forms, which 
will not make their appearance without such conditions. 
We have likewise seen that those erystallizations or for- 
mations are greatly assisted by constant motion. Just on 
the conditions which exist in Holwell Cavern, and under 
these circumstances, I have produced about 200 varieties of 
minerals, exactly resembling in all respects similar ones 
found in nature, as well as some others never before dis- 
covered in nature, nor formed by art. Still, there are a 
vast number of minerals which, in the present state of the 
science, defy the ingenuity of man to imitate, but many 
