AIR. 



It is a law of all action, whether natural or artifical 

 that no change can take place without the exertion of 

 what we call power ; and the power by which the 

 change is effected must always be greater than that 

 which maintained the substance or substances in the 

 state out of which they were changed, or, in other 

 words, greater than that by which they were brought 

 into that state. As for example, it always takes a 

 greater exertion of power to separate two substance 

 chemically coinbined than it did to combine them and 

 hold them in combination ; and so also it takes a 

 greater degree of power to combine them anew than 

 that by which they were separated and held asunder. 



This is the general law of all natural action, indeed 

 of all action whatsoever ; and it is necessary that 

 every one wishing to have scientific knowledge ol 

 nature, or indeed of any thing else, should have the 

 clearest possible notions respecting it. A state of 

 perfect equality in power would be a state of total 

 inaction of universal death and quiescence ; and a 

 creation of which that were the law could produce 

 nothing and would be good for nothing. That the 

 stronger only can vanquish, and the weaker only can 

 be vanquished, is, when the facts are known, the law 

 equally of the whole and of all the parts down to the 

 most minute ; and it is a law to which there are not 

 even the most temporary exceptions. Ignorance of 

 this law is the cause of all the failures which take 

 place in human attempts ; and impossibility is only 

 another name for its attempted violation. This alone 

 would justify the length at which the principle of the 

 law has been stated, and strongly recommend it to the 

 most attentive consideration. I3ut if it were our pro- 

 vince to treat of the practical application of mechani- 

 cal and chemical science, we could fill volumes with 

 instances in which human ingenuity has been most 

 lamentably wasted, solely from ignorance of or in- 

 attention to this universal and most important law. 



It must be borne in mind, however, that time is an 

 element as well as intensity ; and though we are 

 not warranted in saying that the effective power is 

 always the product of the time and the energy, yet 

 our inability of doing so depends on the nature of 

 the energies and on the contingencies on time, rather 

 than upon any improbability in the doctrine 

 itself. Before returning to our proper subject, the 

 air, it may not be amiss to mention an instance or 

 two, in order to fix this, the most important truth, 

 perhaps, in the whole three kingdoms of nature, upon 

 the minds of those readers who are not accustomed 

 to such considerations. Then, in the first place, the 

 timber of an oak tree, treated with proper skill, suf- 

 fices, in the course of not very many hours, to convert, 

 by the help of the workman and his tools, a lump of 

 iron-stone into a steel hatchet. The tree may have 

 taken a hundred years in growing, and the iron-stone 

 a longer time in consolidating ; but the rapid decom- 

 position of the tree the undoing of that which it did 

 during its growth, affords a power concentrated in 

 intensity from being shortened in time, before which 

 the stubbornness of the iron-stone must give way. It 

 may be that the oak is first burnt into charcoal in a 

 smouldering fire, and the iron-stone roasted in a slow 

 oven to clear it of sulphur ; but the object of these 

 operations is to get rid of volatile substances which 

 would scatter the heat and also the substances acted 

 upon. Again, a very small quantity of gunpowder, 

 duly applied and ignited, will rend in pieces many 

 tons of the toughest rock ; and we cease to wonder at 



the result when we reflect upon the length of time 

 during which (lie charcoal was growing, the saltpetre 

 forming, the sulphur subliming by volcanic heat, and 

 the labour of making the powder, all of which were 

 undone in that momentary explosion. 



Now, when we turn from these instances of strong 

 natural action, and consider the air, formed of ingre- 

 dients which can be mixed or separated instantane- 

 ously and without effort, save that which is necessary 

 to overcome the inertia of the particles ; and that 

 these particles are so small and light that the number 

 of them in a grain probably exceeds that of the grains 

 in the mass of the earth, and that they are all but 

 self-mobile, we see what a wonderful element the 

 Creator has prepared for his creatures. From tin- 

 giant of the forest to the mucor on the humid stone 

 from the whale in the ocean and the elephant in the 

 jungle to the viewless animalcule, which prints doubt 

 upon the finest microscope, there is a wonderful range 

 of organs, in magnitude and in energy, but the air is 

 equally obedient to them all ; and the little things, 

 of which a thousand may be lifted on a pin's point, 

 or hung in a drop "upon the most slender cobweb, 

 find themselves as competent to receive life from that, 

 as those which shake the earth with their tread, or 

 cause the ocean to boil with their plunge. 



And the same minuteness of division enables the 

 air to find its way to every place where its presence 

 can be required. There bores not a worm, there de- 

 scends not a root, so deeply into the ground as that 

 the air cannot reach it, so that to all that grow and 

 live above the surface, on the surface, or under the 

 surface, the air is the breath of life ; all are equally 

 refreshed by it, and the most feeble is no more fatigued 

 by it than the most powerful. 



To us, the water, whether of the lakes and streams 

 or of the ocean, seems a compact and continuous 

 liquid ; and neither the eye nor the microscope can 

 find in it any pores or interstices ; and yet we have no 

 reason to doubt that air freely finds its way into the 

 water, to the greatest depth from which the plummet 

 ever brought up a bit of living weed, or a shell con- 

 taining a living animal, or indeed " deeper far than 

 plummet ever sounded ;" nay, it is not impossible that 

 the air pervades the whole mass of the globe, liquid 

 or solid, to its very centre. 



The manner in which animals and plants, of dif- 

 ferent classes and habits, make use of the air, varies 

 so much, that the explanations can be best given in 

 the accounts of the creatures themselves ; but it may 

 be stated as a general truth, to which there is no known 

 exception, that all of them, in respiration, or in that 

 process which answers the same purpose, use the air 

 itself, and do not, by that process at least, elaborate 

 it, or any of its ingredients, out of other substances. 

 It may be used rapidly or slowly, the quantity may 

 be great or it may be small, and these will always 

 be found connected with the general activity of 

 the other systems in the animal ; but still it is air that 

 is wanted, and it is wanted to some extent, at least, 

 for every living creature, plant, or animal. If the 

 creature lives on land, then the air is taken into the 

 lungs of the animal ; and the plant may be considered 

 as possessing lungs all over its living surfaces ; and 

 though it is not made out that there is a respiratory 

 system within plants, anymore than that there is a cir- 

 culating one, still there is air in the interior of most 

 plants, perhaps of all ; and they may absorb or other- 

 wise act upon that air at the coats of their vessels just 



