He has given a clear view of the Abbé Haüy's curious discoveries regarding the six primitive figures or solids which form the bases of all crystals--the three integrant particles or molecules which constitute the primitive forms, and of the theory by which it is shown how the immensely numerous and diversified secondary or actual forms arise out of these few elementary figures. This is certainly one of the most singular and acute discoveries of our age. It is true, there is a difference of opinion among mineralogists as to the practical use of crystallography in the discrimination of minerals. Some dwell upon it with excessive minuteness, and others seem restless and impatient of its details. The truth seems to be, that those who understand it, derive from it (wherever it is applicable) the most satisfactory aid; and it requires only a moderate knowledge of geometry to understand its principal outlines. On the other hand, it is no doubt possible, in most instances, to dispense with its aid, and to discriminate minerals by their other properties. Of the external and physical characters of Mr. Werner, Mr. Cleaveland has given a clear account, combining into the same view the fine discriminations of the French authors, particularly regarding refraction, phosphorescence, specific gravity, electricity, chatoyement, and magnetism. The same may be said of the chemical characters. We do not know a more satisfactory and able view of the characters of minerals than Professor Cleaveland has exhibited. We would however ask, whether, in enumerating the kinds of lustre, the term _adamantine_ should not be explained, as it is not understood by people in general, while the terms denoting the other kinds are _generally_ intelligible; whether in the enumeration of imitative forms, _lenticular_ and _acicular_ should not rather be referred to the laws of crystallization; whether _reniform_ and _mamillary_ are synonymous; whether _sandstone_, as being a mere aggregate of _fragments_, is a good instance of the _granular_ fracture; whether in its natural state (at least the common ore of nickel) is _ever_ magnetic, till _purified_, and whether cobalt is _ever_ magnetic unless _impure_. Professor Cleaveland's remarks on _fracture_ are uncommonly discriminating and instructive, and would lead a learner to a just comprehension of this important point in the characters of minerals.