Professor Haussmann on Metallurgic Crystallography. 351 
.J 
being perfect, and containing the rudiments of the rest. The in- 
ternal planes of the tetraedrons are ladder-formed, and are fre- 
quently ornamented with lesser excavated tetraedrons. The exca- 
vated tetraedrons are frequently so intimately combined, as to 
have the points of the one running into the cavities of the other ; 
so that the trilateral elongated pyramids, or trilateral tetraedrons 
with acute apices, are unobserved. Two or four excavated tetrae- 
drons are sometimes .combined in simple trilateral or quadrilate- 
ral pyramids ; the greater number of which occur in masses, so 
as to become elongated pyramids or elongated prisms. 
CONCLUSION. 
From the series of observations which have been now made, 
and to which I hope to be able to make additions hereafter, some 
general conclusions may be drawn. 
1. By an examination of metallurgical productions, we arrive 
at the knowledge of several crystalline substances, which are not 
native formations, and of mixed substances containing determi- 
nate proportions, which are also artificially produced ; we dis- 
cover, also, several crystalline substances or formations, hitherto 
unknown. 
2. We learn that several crystalline formations are produced, 
by different metallurgical processes. 
3. That some substances obtain the same crystalline forms by 
a dry, as well as by a wet process, and from metallurgical pro- 
cesses as well as from nature. 
4. We see that metallurgical productions frequently afford 
opportunities of studying the formation of crystals ; and from 
these metallurgical productions we learn, that crystalline forma- 
tion follows the same laws, whether it takes place by a dry or by 
a wet process. 
5. From these conclusions it may easily be deduced, that not 
only the science of crystallography, but the other branches also 
of anorganology, and even metallurgy itself, may derive advan- 
tage from an investigation into substances produced by metallur- 
gical processes *. 
* The above is an abridgment of a printed memoir, sent to us by Professor 
Haussman, and which, we believe, has been lately published by the Royal Society 
of Gottingen, 
