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.

Division of Natural History into three branches—subdivision into two—distinction between organized and unorganized bodies—Minerals, simple and compound.

Elementary bodies—compound substances. Definition of a simple Mineral—integrant molecule—component (or elementary) molecules.

Ex. gr. Sulphuret of Iron—carbonate of Lime. Definition of a compound Mineral—ex. gr. Granite.

Distinction between Mineralogy and Geology—mode of pursuing the study of Mineralogy—want of a precise arrangement—number of species inconsiderable.

Method of identifying species—characters of Minerals—terms used in Mineralogy—subdivision of Physical and Chemical characters.

ESSENTIAL CHARACTER

Composition of the integrant molecule—analysis of Minerals—estimation of the essential and accidental ingredients.

GEOMETRIC CHARACTERS

Crystallization—definition of a crystal—to every Mineral a certain series of crystals—ex. gr. Quartz—some forms common to different species.

Secondary crystals artificially constructed by the addition of integrant molecules to a primitive nucleus.

Laws of decrement:

1. 1st. On the Edges—ex.gr. Rhomboidal and pentagonal dodecahedrons derived from the Cube.

2. 2d. On the Angles—ex. gr. Regular octohedron derived from the Cube.

3. 3d. Mixed decrements.

4. 4th. Intermediate decrements.

Subtractive molecules.

Compound secondary crystals—ex. gr. Icosahedron.

Regular pentagonal dodecahedion and regular icosahedron incompatible with the laws of crystallization.

Number of crystalline forms—laws of decrement limited in nature.

Natural mode in which crystals are formed—from solution—from fusion.

Progress of crystallography—opinions of Linnæus—Tournefort—Romé de l'Isle—Bergman—Haüy.

All crystals of the same species reducible to one form—cleavage—ex. gr. Rhomboid extracted from all crystals of carbonate of lime—some primitive forms common to different species—Structure—Fracture.