(136.) It has been shown, in the preceding chapter, that there are three modes by which the objects of nature may be classified; and that one of these — that is, the natural system — is alone conducive to the advancement of natural history as a physical science. To this, therefore, we shall hereafter confine our attention; because the principles of this science must be discovered by a similar series of inductive generalisations to those used in every department of natural philosophy, “through which one spirit reigns, and one method of enquiry applies.”

(137.) Let us suppose, then, that an entomological student, with a well-filled cabinet of unarranged insects, having his mind well stored with those simple facts regarding their structure and economy which he is to look upon as solid data — let us suppose him to commence the arrangement of the objects before him, according to what he thinks their true affinities, and with a view of verifying or discovering their natural arrangement. He commences by placing, one after the other, those species which bear the greatest mutual resemblance; and for a time he proceeds so satisfactorily, — he finds the several links of the chain, as it were, fit into each other so harmoniously, — that he begins to think the task much easier than he at first expected; and that he will not only be able to prove, by these very examples before him, the absolute connection of one given genus to another, but also to demonstrate that the scale of nature is simple — that is, passing in a straight line from the highest to the lowest organised forms.

(55.) I. The nature and objects of the science having now been sufficiently explained, we may consider the advantages which more peculiarly attend its prosecution, independent of those which have already been noticed, in a general way, as belonging to all intellectual pursuits. We shall enumerate these advantages under distinct heads, because some are applicable only to particular persons, objects, or circumstances; and because, by so doing, we may excite an interest and a love for these enquiries in the minds of many persons, who imagine they have neither the abilities to study, nor the means of adopting such pursuits, and of others who think they are in no way interested in them. We shall therefore look to natural history — 1. as connected with religion; 2. as a recreation; 3. as affecting the arts and common purposes of life; and, 4. as an essential accomplishment to the traveller.

(56.) All the advantages that result from science, are comprehended under two distinct classes: — 1. Either they relate to our worldly prosperity, by opening new sources of wealth, of convenience, or of luxury; or, 2. they administer to intellectual gratification and our spiritual welfare. When, therefore, we speak of the advantages attending the prosecution of this science, we must readily admit that they chiefly belong to the latter class, although they may, in a limited degree, be applied to the former.

(1.) To form a just estimate of the relative position of any science at a given period, it is necessary that the prominent events in its history be rightly understood. It seems, therefore, expedient to commence this discourse with a slight sketch of the rise and progress of zoological science; or, more properly, of the progressive discovery of the forms, structures, and habits belonging to the animal world; a world replete with such an infinity of beings, each possessing so many peculiarities of habit and economy, that, notwithstanding the united efforts of human research for thousands of years, there is not one of them whose history, as yet, can be pronounced complete.

(2.) The vast and diversified field of enquiry over which zoology extends, and the many distinct portions into which it is now distributed, render it extremely difficult to embrace the whole in one general exposition. For it has happened, that at one period of time while our knowledge has made gigantic progress in one department, it has been stationary, or even retrograde, in others; and at another epoch we find that original research has been abandoned, and the technicalities of system and nomenclature alone regarded. To meet the first difficulty, and to preserve, nevertheless, a connected narrative, it seems advisable to treat the subject historically; and pre-supposing certain epochs in this science, to detail the peculiar characteristics of each.