« ПредишнаНапред »
and squeeze the unwary animal to death.” a Here, under a new model, we recognise the ancient plan of nature, viz. the relation of parts and provisions to one another, to a common office, and to the utility of the organized body to which they belong. The attracting syrup, the rows of strong prickles, their position so as to interlock, the joints of the leaves; and what is more than the rest, that singular irritability of their surfaces, by which they close at a touch ; all bear a contributory part in producing an effect, connected either with the defence or with the nutrition of the plant.
When we come to the elements, we take leave of our mechanics; because we come to those things, of the organization of which, if they be organized, we are confessedly ignorant. This ignorance is implied by their name. To say the truth, our investigations are stopped long before we arrive at this point. But then it is for our comfort to find, that a knowledge of the constitution of the elements is not necessary for us. For instance, as Addison has well observed, “ we know water sufficiently, when we know how to boil, how to freeze, how to evaporate, how to make it fresh, how to make it run or spout out, in what quantity and direction we please, without knowing what water is.” The observation of this excellent writer has more propriety in it now, than it had at the time it was made : for the constitution, and the constituent parts, of water, appear in some measure to have been lately discovered; yet it does not, I think, appear, that we can make any better or greater use of water since the discovery, than we did before it.
We can never think of the elements, without reflecting upon the number of distinct uses which are consolidated in the same substance. The air supplies the lungs, supports fire, conveys sound, reflects light, diffuses smells, gives rain, wafts ships, bears up birds. 'EĚ üdatos ta narta: water, besides maintaining its own inhabitants, is the universal nourisher of plants, and through them of terrestrial animals ; is the basis of their juices and fluids; dilutes their food; quenches their thirst; floats their
* Smellie's Phil. of Nat. Hist. vol. i. p. 5.
burdens. Fire warms, dissolves, enlightens : is the great promoter of vegetation and life, if not necessary to the support of both.
We might enlarge, to almost any length we please, upon each of these uses : but it appears to me almost sufficient to state them. The few remarks, which I judge it necessary to add, are as follow :
I. Air is essentially different from earth. There appears to be no necessity for an atmosphere's investing our globe; yet it does invest it: and we see how many, how various, and how important are the purposes which it answers to every order of animated, not to say of organized, beings, which are placed upon the terrestrial surface. I think that every one of these uses will be understood upon the first mention of them, except it be that of reflecting light, which may be explained thus :- If I had the power of seeing only by means of rays coming directly from the sun, whenever I turned my back upon the luminary, I should find myself in darkness. If I had the power of seeing by reflected light, yet by means only of light reflected from solid masses, these masses would shine indeed, and glisten, but it would be in the dark. The hemisphere, the sky, the world, could only be illuminated, as it is illuminated, by the light of the sun being from all sides, and in every direction, reflected to the eye, by particles, as numerous, as thickly scattered, and as widely diffused, as are those of the air.
Another general quality of the atmosphere is the power of evaporating Auids. The adjustment of this quality to our use is seen in its action upon the sea. In the sea, water and salt are mixed together most intimately; yet the atmosphere raises the water, and leaves the salt. Pure and fresh as drops of rain descend, they are collected from brine. If evaporation be solution (which seems to be probable) then the air dissolves the water, and not the salt. Upon whatever it be founded, the distinction is critical ; so much so, that when we attempt to imitate the process by art, we must regulate our distillation with great care and nicety, or, together with the water, we get the bitterness, or, at least, the distastefulness, of the marine substance: and, after all, it is owing to this original elective power in the air, that we can effect the separation which we wish, by any art or means whatever.
By evaporation, water is carried up into the air ; by the converse of evaporation, it falls down upon the earth. And how
does it fall? Not by the clouds being all at once re-converted into water, and descending like a sheet; not in rushing down in columns from a spout; but in moderate drops, as from a colander. Our watering-pots are made to imitate showers of rain. Yet, à priori, I should have thought either of the two former methods more likely to have taken place than the last.
By respiration, flame, putrefaction, air is rendered unfit for the support of animal life. By the constant operation of these corrupting principles, the whole atmosphere, if there were no restoring causes, would come at length to be deprived of its necessary degree of purity. Some of these causes seem to have been discovered, and their efficacy ascertained by experiment. And so far as the discovery has proceeded, it opens to us a beautiful and a wonderful economy. Vegetation proves to be one of them. A sprig of mint, corked up with a small portion of foul air, placed in the light, renders it again capable of supporting life or flame. Here, therefore, is a constant circulation of benefits maintained between the two great provinces of organized nature. The plant purifies what the animal has poisoned ; in return, the contaminated air is more than ordinarily nutritious to the plant. Agitation with water turns out to be another of these restoratives. The foulest air, shaken in a bottle with water for a sufficient length of time, recovers a great degree of its purity. Here then again, allowing for the scale upon which nature works, we see the salutary effects of storms and tempests. The yesty waves which confound the heaven and the sea, are doing the very thing which was done in the bottle. Nothing can be of greater importance to the living creation, than the salubrity of their atmosphere. It ought to reconcile us therefore to these agitations of the elements, of which we sometimes deplore the consequences, to know that they tend powerfully to restore to the air that purity, which so many causes are constantly impairing.
II. In Water, what ought not a little to be admired, are those negative qualities which constitute its purity. Had it been vinous, or oleaginous, or acid; had the sea been filled, or the rivers flowed, with wine or milk; fish, constituted as they are, must have died : plants, constituted as they are, would have withered : the lives of animals which feed upon plants must have perished. Its very insipidity, which is one of those negative qualities, renders it the best of all menstrua. Having no taste of its own, it becomes the sincere vehicle of every other.
Had there been a taste in water, be it what it might, it would have infected every thing we ate or drank, with an importunate repetition of the same flavour.
Another thing in this element, not less to be admired, is the constant round which it travels; and by wbich, 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, which, penetrating into the crevices of the hills, supply springs; which springs flow in little streams into the valleys; and there uniting, become rivers; which rivers, in return, feed the ocean. So there is an incessant circulation of the same Auid: and not one drop probably more or less now than there was at the creation. 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 fertilize 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 inhabitants; minister to as large an aggregate of enjoyment. The land only affords a habitable surface; the sea is habitable to a great depth.
II. Of Fire, we have said that it dissolres. 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 say, 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; universal 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 carth without air; nor exist, as water, without fire.
IV. Of Light (whether we regard it as of the same substance with fire, or as a different substance) it is altogether superfluous to expatiate upon the use. No man disputes it. The observations, therefore, which I shall offer, respect that little which we seem to know of its constitution.
Light travels from the sun at the rate of twelve millions of miles in a minute. Urged by such a velocity, with what force must its particles drive against (I will not say 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 shatter 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 is easy to prove. A drop of tallow, expended in the wick of a farthing candle, shall send forth rays sufficient to fill a hemisphere of a mile diameter; and to fill it so full of these 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 sun, we cannot estimate ; but the immensity of the sphere which is filled with particles, even if it reached no farther than the orbit of the earth, we can in some sort 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 spissitude of the sun's rays at the earth is such, that the vumber 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.
It has been observed to me by a learned friend, as having often struck his mind, that, if light had been made by a common artist, it would have been of one uniform colour: 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.