220 KOENIG—ARTIFICIAL PRODUCTION OF CRYSTALS. [June1, 
The incubator consists of a piece of combustion tubing (T), closed 
at one end. The length is unimportant since only about three 
inches of it are in actual use. I have varied the diameter from 
three-eighths to three-fourths inch with no apparent difference in 
the action. The crystals do not grow any larger in a large tube 
than in a small one. Around the tube is wound a very thin plati- 
num wire (W), beginning at the closed end. In order to keep the 
coils separated I laid three strips of thin asbestos paper (E) length- 
wise upon the glass and then began winding. The first turn returns 
to the start, a twist is made, and thus a well-fixed start is secured 
= 7 a 
iNET 
which will prevent the wire from slipping. The pitch of the thread 
will be governed by the maximum of heat desired. This will be 
variable with different metals and may be varied even for the same 
metal, as I have frequently done, the variation being between one- 
eighth and one-thirty-second of an inch. The last coil is secured 
in the same way as the first. Twoinches of winding were mostly 
sufficient. Whenever the glass gets to full red heat the wire will 
fuse into it and will be broken in unwinding. To avoid this spoil- 
ing of the wire it would be the best thing to cover the whole glass 
surface with the asbestos sheet. But doing so would also prevent 
the observation of the phenomena occurring within. One might 
as well, or even preferably, use a porcelain tube. One would have 
to forego the great pleasure of seeing the so-called inanimate things 
