1903.| KOENIG—ARTIFICIAL PRODUCTION OF CRYSTALS. 229 
pyramidal faces are hollow (see Dr. Wright’s Fig. 3). The dark 
gray crystals are surrounded at the base by a fringe of sz/ver- white 
crystals of the thin plate type. It happened that the exposure 
began about 9 A.M. ona Saturday morning. At.6 P.M. the crop 
of crystals had developed finely, but I hoped that they would 
become extra large by longer exposure. On Sunday I was prevented 
from going to the laboratory, and on my arrival on Monday I found 
the incubator barely warm to the touch. The storage battery had 
run down over Sunday, and to this accident we owe this beautiful 
and interesting preparation which I now hold in my hand. On 
seeing the silver-white crystals I thought, first thing, that I was 
beholding a silver arsenide, but the analysis proved my judgment to 
have been in error. 
The composition is 
Cui== 80.49 91/63, 5 1.2773 
Ag == 2:60):3107.6'—= 0.0242 t #3085 
As sl Olosi75) 0.2257 
Hence the ratio: 
(CwAg): : As = '5.77.4 1 == 62 
This substance then is argentoalgodonite. 
The dark gray crystals have the composition : 
Cu = 70.40 
Ap .2.20 
(By difference) As = 27.30 
100,00 
This is the ratio: 
(CuAe)s As == 3705 
or what I will name argentodomeykite, which we shall, sooner or 
later, find undoubtedly as a natural mineral. But how about the 
algodonite? In no other experiment was it observed. Since the 
form of the crystals is identical with the argentodomeykite, I ven- 
ture to assert that the algodonite is pseudomorphous after the 
domeykite, and owes its existence to a retrogressive process in this 
way: when the temperature was slowly going down (with the cur- 
rent from the battery) the arsenical atmosphere became more and 
more rarefied with the greed of the metallic copper still active. 
Hence the copper began to draw the arsenic from the nearest 
