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XXIX. — Account of the Method of Drawing 
Crystals in True Perspective, followed in the 
Treatise on Mineralogy of Professor Mohs. 
By W. Haidinger, Esq. of Vienna, F.R.S.E. Member 
of the Wernerian Society, &c. 
{Read Uth May 1825.) 
,A.LL those who have devoted their attention to the study 
of Crystallography, must have experienced many difficulties 
arising from the want of a proper method of drawing the 
projections of crystals, an object which, at the same time, 
should be effected with perfect ease, and with sufficient 
accuracy. Those who already possess the required crys- 
tallographic knowledge, will, indeed, very soon be capable 
to draw up rules for themselves ; but this knowledge is not 
yet so generally diffused as it deserves, both for the influ- 
ence it is likely to take in the progress of the science, and 
for the wonderful regularity of nature which it displays. 
The very attempt of drawing crystalline forms is insepar- 
able from a close examination of these, and therefore a step 
forwards in studying crystallography ; we may acquiesce 
in giving a vague verbal description of a crystal, but a 
vague representation of its figure seems to inply some im- 
