222 KOENIG—ARTIFICIAL PRODUCTION OF CRYSTALS. [June1, 
thermic energy is made part of the circuit. A water resistance 
answers very well if a Mariotte’s bottle be provided to keep the 
water level, and if the one wire be fastened to a swivel ; the latter 
arrangement permits a quick and easy modification to ;)455 amps. 
In my work with the incubator a drum resistance coil with roller 
contact was used. The apparatus was placed into a dark room in 
which the faintest glow could be seen and thus the lower limit of 
temperature was probably 450° C., with the upper limit of C. 500° to 
700°. The most satisfactory range for domeykite is about 600° C. 
AIMS OF THE INVESTIGATION. 
At the start the aim was not so much the mere production of 
domeykite crystals, as the demonstration that nickel and cobalt 
might replace copper in’the molecule without changing the symme- 
try, in other words to establish the isomorphous character of 
domeykite and mohawkite. This original scope became at once 
wider, when the results showed the ease with which domeykite was 
formed in good crystals. The action of arsenic upon iron, lead, 
silver, cobalt, nickel was included and equally satisfactory results 
were fondly hoped for. 
A still farther circle could be described by drawing in antimony 
since silver was known to unite with antimony as Ag,S,. The 
hopes were not realized. Under other conditions perhaps better 
results may be obtained, at least in somecases. I am referring here 
to the action in vacuo. Up to this time I have not tried the 
vacuum, so much other work is constantly crowding in. I will not 
pre-empt work in this line and shall gladly see any colleague step 
in to take up this undoubtedly highly interesting work. 
1. ACTION OF ARSENIC VAPORS UPON COPPER IN THE INCUBATOR 
—DoMEYKITE. 
a. Coarse copper turnings were placed in the tube (C. Fig. 2) so 
that about three-fourths inch of free space were left between the cop- 
per and the asbestos plug P, and the contact wires were so placed that 
the evaporation of the arsenic was fairly rapid, whilst the tempera- 
ture of copper remained near the lower limit of say 500° C. Soon 
one saw shooting out from the copper very thin, brilliant leaves. The 
direction of growth was parallel with the tube’s axis. The growth 
keeps up until the entire free space is filled with the bright crystal 
aggregate. The latter looks much like sublimed arsenic, and that I 
