ABSTRACT
Having now passed through the entire circle of terrestrial inorganic nature, – having considered our planet in respect to its form, its internal heat, its electromagnetic charge, its polar luminous effusions, the reaction of its interior on its variously composed crust, and finally the phænomena of its oceanic and atmospheric envelopes, – the view which we have essayed to trace in broad and general outlines might be regarded as complete, and would be so according to the limitation formerly adopted in physical descriptions of the globe. But the plan which I have proposed to myself has a more elevated aim, and I should regard the contemplation of nature as deprived of its most attractive feature, were it not also to include the sphere of organic life with its many gradations of development. The idea of life is so intimately connected with the moving, combining, forming, and decomposing forces which are incessantly in action in the globe itself, that the oldest mythical representations of many nations ascribe to these forces the production of plants and animals, and represent the epoch in which the surface of our planet was unenlivened by animated forms, as that of a primeval chaos of conflicting elements. But investigations into primary causes, or into the mysterious unresolvable problems of origin, do not enter into the domain of experience and observation; nor has the obscure commencement of the history of organisation a place in the description of the actual condition of our planet. These reservations once made, it should still be noticed in the physical description of the world, that all those substances which compose the organic forms of plants and animals are also found in the inorganic crust of the earth; and that the same powers which govern inorganic matter are seen to prevail in organic beings likewise, combining and decomposing the various substances, regulating the forms and properties of organic tissues, but acting in these cases under conditions yet unexplained, to which the vague term of ‘vital phænomena’ has been assigned, and which have been systematically grouped according to analogies more or less happily imagined. Hence has arisen a tendency of the mind to trace the action of physical forces to their extremest 526limits in the development of vegetable forms, and of those organisms which are endowed with powers of voluntary motion: and here, also, the contemplation of inorganic nature becomes connected with the distribution of organic beings over the surface of the globe, i.e. the geography of plants and animals.
