The present duty of a systematical inquiry, is to describe objects and actions which cannot all yet be classed under general divisions and laws; and it cannot avoid proposing analogies and inferences which it is unable to prove; while it must also make use of proofs which are themselves to be proved hereafter, or prove several laws by one or more facts, or the reverse; thus necessarily becoming entangled among future and retrospective references. Hence, the order which would be desired, cannot be adopted. And hence also it may be useful to give a sketch of an order, which, however dry and repulsive it may appear, will serve to indicate the catenation of the facts and inferences. The materials of this inquiry areObjects and Actions; the result constitutes Inferences ; and these are retro spective, as well as present and future. The Retrospect is the material for a Theory of the Earth. OBJECTS. The Objects are the Materials of the Earth. The Materials are, Rocks and Fragments. The Rocks are, Stratified and Unstratified. Rocks and Fragments are formed of the same sub stances. The substances are simple earths, including oxydes, or minerals. Rocks, and the larger Fragments, are composed of Earths or of Minerals, and of Animal and Vegetable matters compacted. They are compacted by Mechanical approximation, or by Chemical action, or by both united.