Esq., Lecturer on Chemistry to the Hunteriau School of Medicine. (A Lecture delivered before the Royal Medico-Botanical Society Of London.)

At the request of my friend, the learned Professor of Chemistry to this society, I have been induced to throw together, into a connected form, a few facts, tending to show how the sciences of chemistry, geology, and meteorology, are by means of botanical geography and structural botany mutually related to each other. It was with a feeling of diffidence that I approached such a subject as this, considering how very limited my knowledge must necessarily be upon many of the topics which it includes; and this feeling was in no way diminished, when I found that this grouping of the sciences led me within the portals of a new science, which is founded upon more enlarged generalisations than any other that has gone before it, and this because it is the last product of the rearing and creative faculty, applied to a reviewal of the more extended surveys of the natural world which we have now, coupled with the accurate and profound knowledge of the labors and advances of philosophers during past years.

Natural history geography is the science to which I allude: a science which, besides geographical description, includes the general phenomena of the present life of the globe, in reference to their connection and mutual dependence. For the most part, this science is a production of the German schools. Schlegel, in his "Concordia," in 1820, put forth some of the germs of this branch of natural philosophy, (or rather this combination of branches;) in seven years afterwards, in 1827, appeared those memorable lectures on the "Philosophy of Life," embodying more extended and perfect views than had yet been suggested, even although, as early as 1806, and perhaps before, some of the sketches which at present form the "Aspects of Nature," were publicly delivered by their illustrious author. At the end of the fourth lecture on the "Philosophy of Life," we find expressed one of those truths to which I have just alluded: - "An exalted view and understanding of nature consists in its being contemplated not merely as a dynamical play of reciprocal forces, but historically in its course of development as a commencing life, perpetually relapsing into death, ever disposed to sleep, and only painfully raising itself, or rather raised and lovingly guided through all the intermediate grades into life.

But beneath the huge tombstone of outward nature, there sleeps a soul not wholly alien, but half akin to ourselves, which is distracted between the troubled and painful reminiscences of eternal death, out of which it issued, and the flowers of light, which are scattered here and there on this dark earth as so many lively suggesters of a heavenly hope." Perhaps in a more eminent degree, Carl Bitter aided in forwarding the science of natural history geography. He, as well as Schlegel, recognised the vitality of the globe. Our views on this subject have to a considerable degree been enlarged and strengthened by the translation into English of the beautiful comparative physical geography of Arnold Guoyot - a work that cannot be too extensively read. But after all, there is one name which is more especially connected with this science - a name which has been by Professor . Forbes termed its organiser, as well as originator: I allude to the Baron Alexander Ton Humboldt.

Natural history geography may be regarded as including, among other things, the different chemical, geological, and general physical relations which have modified the distribution of plants and animals - of plants, because the conditions of a thriving vegetation are so various that under certain circumstances there springs a peculiir flora, giving a characteristic scenery to a country, and so influencing the mind. But such a distribution is also an index to the geology, because certain plants require a certain soil, and the quality of the soil depends mainly upon the geological formations; to the meteorology, because certain plants require particular amounts of heat and moisture. It is the proper province of chemistry to tell us the constitution of the soil - to show what ingredients are contained in a plant from the analysis of its ashes: so that chemistry, geology, and meteorology are, by means of vegetation, brought into a more intimate relationship. We can, however, look at a plant as the theatre for the display of certain physical actions - as an appabenefits he has conferred upon science are very great, for this reason: they are twofold in their nature.

Besides the actual results of his own labors - and they are many and various - he opened a new field for the direction of the energies of other men. Were his theories all wrong - his researches all false - still, if by them the spirit of inquiry was aroused, in the end he would benefit science. The past history of inductive science confirms this statement. We cannot now afford time to trace the origin and rise of agricultural chemistry, but must be content with a slight glance at it as it now exists - a product of the mental exertions of the German professor.

The first point of importance upon looking at the chemical phenomena of vegetation, is, that there are various actions always going on in a plant, owing to the decomposition of certain portions of its structure, or of the materials whence it derives its food - actions extremely different to those mechanical actions to which I have before alluded. They are changes which at first sight appear to be strictly chemical, and which are very often confounded with each other. I refer to the decomposition of carbonic acid and of water - to the absorption of oxygen during darkness - to the emission of carbonic acid during the night. The decomposition of carbonic acid and of water may be designated as chemico-physical action; the absorbtion of oxygen during the night is entirely a chemical process; the emission of carbonic acid being, on the other hand, a purely mechanical operation.