HINTS TO STUDENTS OF GEOLOGY. BY PETER A. BROWNE, ESQ. NO. I. The word "_science_," in its most comprehensive sense, means "knowledge." In its general acceptation, it is "knowledge reduced to a system;" that is to say, arranged in regular order, so that it can be conveniently taught, easily remembered, and readily applied to useful purposes. An _art_ is the application of knowledge to some practicable end,--to answer some useful or ornamental purpose. The sciences, are sometimes divided into the _abstract_ and the _natural_; by the former we are taught the knowledge of reasons and their conclusions; by the latter we are enabled to find out causes and effects, and to study the laws by which the material world is governed. To the abstract sciences belong, first, language, whether oral or written, including grammar, logic, &c.; secondly, notation, including arithmetic, algebra, geometry, &c. Philosophy inquires into the laws that regulate the phenomena of nature, whether in the material or immaterial world; it is generally divided into three classes, two of which are material and one immaterial. The material are, first, those which relate to number and quantity; secondly, those which relate to matter. The immaterial are those which relate to mind. The second class of the material is called "natural philosophy" or "physics," and sometimes the "physical sciences." Natural philosophy, in its most comprehensive sense, has for its province the laws of matter, whether organic or inorganic. These laws may regard either the motions or properties of matter, and hence arises their division into two branches--first, those which regard the _motions_ of matter, which are called _mechanics_; and secondly, those which regard the _properties_ of matter, which are subdivided, and have various names, according to the different objects of investigation. When the inquiry is confined to organized bodies and life, it is called physiology; which is again subdivided into zoology and botany. When it treats of inorganic matter, it is subdivided into chemistry, anatomy, medicine, mineralogy and geology. The principles of natural philosophy rest upon _observation_ and _experiment_. Observation is the noticing of natural phenomena at they occur, without any attempt to influence the frequency of their occurrence. Experiment consists in putting in action causes and agents, over which we have control, for the purpose of noticing their effects. From a comparison of a number of facts, obtained from either observation or experiment, the existence of general laws are proved. The laws of man are complicated; to understand their objects, we are often obliged to take the most circuitous routes; but the laws by which nature governs all her works are beautifully simple, and they are found to lead directly to the end she has in view. To study them, therefore, according to the rules that have been laid down, viz: from observation and experiment, is pleasant and easy. The