s commonly described as that branch of knowledge which treats of the properties of natural bodies, and their actions on one another. This term serves to indicate not one but a cluster of sciences. Those generally comprehended under it are the following, viz.—Mechanics, theoretical and practical; Hydrostatics and Hydrodynamics; Optics; Astronomy; Magnetism; Electricity. There are, in this work, distinct treatises on all these different branches, introduced in the order of the alphabet; whilst the history of the whole is traced, in a connected method, in the Fourth, Fifth, and Sixth Preliminary Dissertations.