itself is maintained, equally free from variation, and from the necessity of interference to prevent variation.

Still farther, not only does one and the same body give support and stability to the system, but furnishes it with the essential requisites of light and heat.

In descending from the contemplation of the whole system to the examination of the globe to which we ourselves belong, we are attended by the same comprehensive wisdom. The air of our atmosphere, which is necessary to the existence of the animal and vegetable world, is composed of two elastic fluids, united in a definite and exact proportion; a proportion so precisely suited to those for whose respiration it was intended, that any difference in the quantity of either ingredient would prove, according to its degree, injurious or destructive. The same air which supplies life and health to the human race, is equally and alone salubrious to every other animal. It might be

expected that the portion of this air which animals return in the alternate motion of the lungs, having performed its service, would prove of no farther utility: but it has been otherwise contrived. This part of the atmosphere, though insalubrious to man, affords the most grateful nourishment to the plants by which he is surrounded; according to which provision nothing is lost, and the constant purity of the air we breathe is preserved.

The same air which in its compound state supports the life of the animal creation, administers also to the comfort and necessities of man in the shape of fire.* Combustion is the decomposition of the atmosphere, a process which, under certain circumstances of temperature, most of the products of the earth have in a greater or less degree the power of effecting; and which is regularly accompanied

*

Though the phlogistic theory still retains some advocates, and the one here alluded to is not without its difficulties, I conceive that its general reception warrants the use I make of it, in a view so rapid and cursory as the present.

by the disengagement of the light and heat for which we have such frequent occasion, when the assistance of the solar rays is either wanting, or inapplicable. The same elastic fluids which perform these important purposes, in another state of composition become the chief constituents of water also. And the result is, that the principal wants of the animal and vegetable world are supplied by three elastic fluids, the peculiar union of which furnishes us with water, fire, and vital air. Neither do these fluids require the interposition of the Creator to supply their constant expenditure. The original mandate of eternal Wisdom provided, as far as we can learn from physical researches, for a world of which we cannot foresee the termination. The simple gasses, disengaged by various natural processes, from the combustibles, vegetables, and different substances which absorb them, are so contrived as to form a natural re-union, and preserve a constant equilibrium.

The same principle of economy and of uni

versality in the means employed to produce the most important results, might be exemplified throughout the whole constitution of our globe. It is no light provision, for instance, that the fertility of the earth is incapable of the decay which the perpetual production of plants might be expected to cause: an effect which is guarded against by the single law, that the destruction of one race of vegetables affords aliment to a fresh succession. By a contrivance equally prospective, the same principle of rarefaction and condensation which purifies the atmosphere, and regulates the temperature of the seasons, raises water in the form of vapour to the clouds, and returns it to the earth as rain, thus diffusing a fertility universally, which would otherwise have been confined to the banks of rivers and it results from these united operations, that the moisture once given at the creation preserves its own equilibrium, without increase, or diminution, or reproduction. It is a part of the same contrivance to furnish the means of communication, and sometimes even of regular communication,

between countries the most widely separated from each other.

I contend, therefore, that the slightest outline of the constitution of the natural world conveys a proof of the most comprehensive wisdom which having determined upon the existence of a habitable system, like ours, according to a certain plan, obtained the purposes required by the simplest conceivable means: and arranged originally the various parts in a regular and dependent order, which should neither be subject to accident, nor require interposition. Indeed, there is sound reason to believe that the argument here touched upon may hereafter be carried to an extent, not only far beyond that to which I have limited it, but beyond that which is compatible with the present state of our knowledge. Every year's experience in natural philosophy diminishes the number of those bodies which are necessarily considered as simple, because they have never been hitherto decomposed, and of course diminishes at the same time the original principles