to designate the Planes of Crystals. 429 
square, which is consistent as far as those two alone are con- 
cerned, but does not exhibit their relation to the others. I think 
the terms I have adopted ensure both these objects. 
The selection of a notation to designate the relations of derived 
forms in crystallometry is by no means unimportant; for, if it be 
constructed with a proper symmetry, and a due regard to the 
analogies which prevail in these forms, it may be made the means 
of facilitating and compressing, im a remarkable degree, our reason- 
ings with respect to the laws and connexions of crystallized forms. 
In fact, it has already been adapted and applied to this end, with 
great imgenuity and success, in the hands of Professor Mohs; and 
there is no one to whom the merit of making this great step in 
the science of mineralogy could more naturally fall, than te one 
possessed of his talents, perseverance, and extraordmary know- 
ledge of the subject. In proportion as this process —I mean that 
of reasoning from our symbols—is valuable and important, it be- 
comes desirable to perfect our notation as much as possible, and 
to carry to the greatest extent which they admit, the analogy 
and simplicity of our symbolical system. It is to be wished that 
perfection m this point should be attained as early as possible, 
in order that we may not have afterwards to alter a notation to 
which men’s minds have become familiarized, and to learn afresh 
the alphabet of the science, which it is an irksome task to have 
even once to acquire. These considerations will excuse the at- 
tempt made in the following paper, and will also account for 
the liberty which I have allowed myself of pointing out some 
anomalies in Professor Mohs’ System of Notation. Without some 
strong reasons, such as those above mentioned, any endeavour to 
alter a notation, in which so much information is embodied, as 
is contained in his treatise, would be inexcusable. Nothing, in- 
deed, can be more likely to produce confusion and unnecessary 
