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Show 4 INTRODUCTION. being, not only with regard to itself ~u.t to its surrounding relations. The analysis of these conditiOns frequently con~ ducts us to general laws, as certain as those that are derived from calculation or experiment. It is only when all the laws of general physics and those which result from the conditions of existence are exhausted, that we are reduced to the simple laws of obser.vation. The most effectual method of obtaining these, is that of comparison. This consists in successively observing the same bodies in the different positions in which nature places them, or in a mutual comparison of different bodies; until we have ascertained invariable relations between their structures and the phenomena they exhibit. These various bodies are kinds of experiments ready prepared by nature, who adds to or deducts from each of them different parts, just as we might wish to do in our laboratories ; showing us, herself, at the same time their various results. In this way we finally succeed in establishing certain laws by which these relations are governed, and which are employed like those that are determined by the general sciences. The incorporation of these laws of observation with the general laws, either directly or by the principle of the con~ ditions of existence, would complete the system of the natural sciences, in rendering sensible in all its parts the mutual influence of every being. To this end, should those who cultivate these sciences direct all their efforts. All researches of this nature, however, pre-suppose means of distinguishing clearly, and causing others to distinguish, the bodies they are occupied with; otherwise we should be continually confounding them. Natural history then should be based on what is called a system of nature; or a great cata- / Iogue in which all created beings have suitable names, may be recognised by distinctive characters, and be arranged in divisions and subdivisions, themselves named and characterised, in which they may be found. In order that each being may be recognised in this catalogue, it must be accompanied by its character: habits or properties INTRODUCTION. 5 which are but momentary cannot, then, furnish charactersthey must be drawn from the conformation. There is scarcely a single being which has a simple character, or can be recognised by one single feature of its conformation; a union of several of these traits are almost always required to distinguish one being from those that surround it, who also have some but not all of them, or who have them combined with others of which the first is destitute. The more numerous the beings to be distinguished, the greater should be the number of traits; so that to distinguish an individual being from all others, a complete description of it should enter into its character. It is to avoid this inconvenience, that divisions and subdivisio~ ls hav~ been invented. A certain number only of neighbourmg bemgs are compared with each other, and their characters. ~eed .only to express their differences, which, by the supposition Itself, are the least part of their conformation. Such a re-union is termed a genus. . !~e same inconvenience would be experienced in distingmshmg genera from each other, were it not for the repetition of the operation in uniting the adjoining genera, so as to form an order, the orders to form a class, &c. Intermediate subdivisions may also be established. This scaffolding of divisions, the superior of which contain t~e ~nferior,. is ca~led a method. It is in some respects a sort of dictio~ary, In W~ICh we proceed from the properties of things to arrive at their names; being the reverse of the common ones, in which we proceed from the name to arrive at the property. When the method is good, it does more than teach us names. If the subdivisions have not been established arbitrarily, but are based on the true fundamental relations, on the essential I resemblances of beings, the method is the surest means of reducin~ the properties of beings to general rules, of expressing them In the fewest words, and of stamping them on the memory. !o re~der it such, we employ an assiduous comparison of bemgs, directed by the principle of the subordination of cha- |