Some explanation seems necessary for having deviated from the plan pursued by my predecessor, in forming his Syllabus of a Course of Lectures for the University.

Having compared the analyses (given by different authors) of various minerals, with the views established by the Atomic Theory, the results of some of these investigations appeared sufficiently important to merit the attention of those who might wish to pursue this subject; but as they are confined to calculations, which it would have been tedious both for a Lecturer to dictate and for his audience to transcribe, it seemed preferable to print them. From a similar consideration, the specific gravities and other properties, which require numerical exposition, have been inserted in the Syllabus. Since, however, these calculations, if added to the notices of the different subjects to be detailed under each species, would have augmented the size of a work of this nature considerably beyond its ordinary limits, it became necessary to deviate entirely from the mode originally adopted by Dr. Clarke. I have therefore supposed the description of each species to be divided into nine different heads, and the objects which each head is intended to include are collected between pages 2 and 6. From these will be selected, for every species, whatever may appear most worthy of engaging the attention ; although reference is seldom made in the remainder of the Syllabus to any but such as embrace the description of some peculiar form, or involve numerical explanation.