224 KOENIG—ARTIFICIAL PRODUCTION OF CRYSTALS. [June1, 
chemical saturation has been reached. To my knowledge, how- 
ever, no experiments have been put on record which absolutely 
precluded the coaction of gasified carbon as CO; I mean that 
the experiments were not carried on in perfectly air-tight vessels. 
Yet, granted even that the solid carbon travels by exchange through 
a bar of iron, the phenomenon is not quite correlated to our 
problem. For if the two were similar then the arsensic would 
have to penetrate to the core of the copper chip without altering 
practically its original shape. But in the specimen Fig. 3 the cop- 
per chip C is perfectly bright metallic copper, even immediately 
under the stylus S. Furthermore all the other metals behaved 
toward arsenic vapors as iron toward carbon: the arsenic penetrates 
Fig. 4 
and crystals do not shoot forth. Copper possesses, therefore, a 
unique tonic mobility. Since copper stands at the head as a con- 
ductor of both heat and electricity, may not this be due to that 
mobility of the ions ? 
6. If acopper chip be placed into the incubator and both resist- 
ance and contact wires be so adjusted that very little arsenic vola- 
tilizes, and that the copper is just below glowing heat, that is dark 
in a perfectly dark room, then the domeykite crystals arise from 
the copper as very thin tabular individuals, often of perfect hex- 
agonal outline. Many of the crystals are only fractional (Fig. 4), 
and in this case look like bristles or spines, always at right angles 
to the surface, or if the latter be curved then the bristles will be in 
radial position. At first’a few scattered crystals will come out, 
always nearest to the supply of arsenic, but later the entire surface 
will become covered with bristles. Under these conditions large 
