250 A new system of Crystallographic Symbols. 
It is believed that a turnout of from 400 to 500 feet radius, with 
flexible moveable rails, will be found to answer a much better purpose 
than those in use at the present time. Several important railroads 
have curves as abrupt as this. On the Baltimore and Ohio railroad 
there are two sharp curves, one of 337, and the other of only 318 
feet radius. 
— 
Art. VIII.—A new system of Crystallographic Symbols; by James 
D. Dana, A. B. 
Tue science of Crystallography has of late years, obtained so great 
importance, that it is justly entitled to be termed the key-stone to 
Mineralogy. Its principles, first fairly developed by the Abbé Haiiy, 
have placed this latter science on a mathematical basis, and have af- 
forded, with but few exceptions, invariable poimts of distinction be- 
tween the different mineral species. With all the exactness, in 
many instances, that attends any branch of mathematical calculation, 
the Abbé Haiiy determined the mutual inclinations, and relative 
situations of secondary and primary planes, and the dimensions of 
the primitive forms of different minerals. The discovery of these 
facts led him to introduce symbols and abbreviated expressions, to 
aid in the description of crystals, by means of which, the position of 
secondary faces may be stated with far more precision than 1s possible 
in a figure. The idea was a happy one. But his system in all its 
particulars does not seem to be beyond improvement. Indeed, im- 
provements have been proposed by some authors, and systems quite 
different adopted by others. ‘That by Mohs is certainly ingenious 
and beautiful. Still there remains one point yet unattained. A sys- 
tem appears to be needed, of which a direct application may be 
made in lettering the figures of crystals. ‘This accomplished, the 
student would be enabled by a mere inspection of the figure, to refer 
any secondary plane to its situation on the nucleus, however disguised 
it might be. Besides, it would be unnecessary in the description of 
a crystal, to accompany the symbolical expression of a plane with 
the letter given it in the figure, (a practice followed by the Abbé 
Haiiy); for the same symbol would be used in both instances. 
To propose a plan for the attainment of the above end, will be 
the object of the following remarks. ‘The great obstacle to it, in the 
systems now in use, is the length of the representative signs of 
