« VorigeDoorgaan »
be admired, is the constant, round which it travels; and by which, without suffering either adulteration or waste, it is continually offering itself to the . wants of, the habitable globe. From the sea are exhaled those vapours which form the clouds. These clouds descend in showers, whicb,,penetrating into the crevices of the hills, supply, springs. . Which springs flow in little streams into the valleys; and, there uniting, become jrivers. , Which rivers, in return, feed the .ocean. So there is an incessant circulation of the./ame fluid; and not one drop probably more or less, now, than there was at the creationf . ;A particle of "water takes its departure from the surface of the sea, in order to fulfil certain important offices to the earth; and having executed the service which was assigned to it, returns to the bosom which it left. , Some have thought ,that we have too 'much water upon the globe; the sea occupying above three quarters of its whole surface. But the expanse of ocean, immense as it is, may be no more than sufficient to. sertilise the earth. Or, independently of this reason, I know not why the sea may not have as good a right to its place as the land. It may proportionably support as many inhabi9 tants; tants; minister to as large an aggregate of enjoyment.- The land only affords a habitable surface; the sea is habitable to a great depth.
III. Of Fire, we have said that it dissolves. The only idea probably which this term raised in the reader's mind was, that of fire melting metals, resins, and some other substances, fluxing ores, running glass, and assisting us in many of our operations, chymical or culinary. Now these are only uses of an occasional kind, and give us a very imperfect notion of what fire does for us. The grand importance of this dissolving power, the great office indeed of fire in the economy of nature, is keeping things in a state of solution, that is to fay, in a state of fluidity. Were it not for the presence of heat, or of a certain degree of it, all
, fluids would be frozen. The ocean itself would be a quarry of ice: univerfal nature stiff and dead.
We see therefore, that the elements bear, not only a strict relation to the constitution of organized bodies, but a relation to each other. Water could not perform its office to the earth without air; nor exist, as water, without fire.
IV. Of Light, (whether we regard it as of. the fume substance with tire, or as a different
2 D 3 substance,) substance,) it is altogether superfluous to ex* patiate upon the use. No man disputes it, The observations, thererore, which I (hall offer, respect that little which we seem to know of its constitution.
Light passes from the fun to the earth in eleven minutes; a distance, which it would take a cannon ball twenty-five years, in going over. Nothing more need be said to show the velocity of light. Urged by such a velocity, with what force must its particles drive against, I will not fay the eye, the tenderest of animal substances, but every substance, animate or inanimate, which stands in its way? It might seem to be a force sufficient to matter to atoms the hardest bodies
How then is this effect, the consequence of such prodigious velocity, guarded against? By a proportionable minuteness of the particles of which light is composed. It is impossible for the human mind to imagine to itself any thing so small as a particle of light. But this extreme exility, though difficult to conceive, it \\ easy tp prove.. A drop of tallow, expended in the wick of a farthing candle, shall shed forth rays sufficient to fill a hemisphere of a mile diameter; and to fill it so full of these , , rays.
rays, that an aperture not larger than the pupil of an eye, wherever it be placed within the hemisphere, shall be sure to receive some of them. What floods of light are continually poured from the fun we cannot estimate; but the immensity of the sphere which is filled with its particles, even if it reached no further than the orbit of the earth, we can in some fort compute: and we have reason to believe, that, throughout this whole region, the particles of light lie, in latitude at least, near to one another. The spiffitude of the sun's rays at the earth is such, that the number which falls upon a burning glass of an inch diameter, is sufficient, when concentrated, to set wood on fire.
The tenuity and the velocity of particles of light, as ascertained by separate observations, may be said to be proportioned to each other: both surpassing our utmost stretch of comprehension; but proportioned. And it is this proportion alone, which converts a tremendous, element into a Welcome visitor. . si Tart -> It has been observed to me by a, learned friend, as having often build his mind', that if light had been made by I common artist,. site would have been of one uuitorm calouhs a D 4 vvherea
whereas, by its present composition, we have that variety of colours, which is of such infinite use to us for the distinguishing of objects; which adds so much to the beauty of the earth, and augments the stock of our innocent pleasures. ',,V: *
With which may be joined another reflection, viz. that, considering light as compounded of rays of seven different colours, (of which there can be no dcfnht, because it can be resolved into these rays by simply passing it through a prism,) the constituent parts must be well mixed and blended together, to produce a fluid, so clear and colourless, as a beam of light is, when received from the fun.