Mrs. Marcet

“ I have said that water forms the chief nourishment of plants; it is the basis not only of the sap, but of all the vegetable juices. Water is the vehicle which carries into the plant the various salts and other ingredients required for the formation and support of the vegetable system. Nor is this all; part of the water itself is decomposed by the organs of the plant; the hydrogen becomes a constituent part of oil, of extract, of colouring matter, &c. whilst a portion of the oxygen enters into the formation of mucilage, of fecula, of sugar, and of vegetable acids. ”

“ When animals are arrived at a state of maturity, and their bones have acquired a sufficient degree of solidity, the phosphat of lime which is taken with the food is seldom assimilated, excepting when the female nourishes her young; it is then all secreted into the milk, as a provision for the tender bones of the nursling.
EMILY.
So that whatever becomes superfluous to one being, is immediately wanted by another; and the child acquires strength precisely by the species of nourishment which is no longer necessary to the mother. Nature is, indeed, an admirable economist! ”

“ Lime combines with most of the acids, to which the carbonic (as being the weakest) readily yields it; but these combinations we shall have an opportunity of noticing more particularly hereafter. It unites with phosphorus, and with sulphur, in their simple state; in short, of all the earths, lime is that which nature employs most frequently, and most abundantly, in its innumerable combinations. It is the basis of all calcareous earths and stones; we find it likewise in the animal and the vegetable creations.
EMILY.
And in the arts is not lime of very great utility? ”

“ It is not the earth that burns, my dear, but the roots, grass, and other remnants of vegetables that are intermixed with it. The caloric, which is produced by the combustion of these substances, makes the earth red hot, and this being a bad conductor of heat, retains its caloric a long time; but were you to examine it when cooled, you would find that it had not absorbed one particle of oxygen, nor suffered any alteration from the fire. Earth is, however, from the circumstance just mentioned, an excellent radiator of heat, and owes its utility, when mixed with fuel, solely to that property. ”

“ We are very far from understanding all the secret resources of nature; but I do not think the spontaneous formation of the crystals, which we call precious stones, one of the most difficult phenomena to comprehend.
By the slow and regular work of ages, perhaps of hundreds of ages, these earths may be gradually dissolved by water, and as gradually deposited by their solvent in the undisturbed process of crystallisation. The regular arrangement of their particles, during their reunion in a solid mass, gives them that brilliancy, transparency, and beauty, for which they are so much admired ”

“ When we are able to ascertain the nature of a substance by both these methods, so that the result of one confirms that of the other, we obtain the most complete knowledge of it that we are capable of acquiring. This is the case with water, with the atmosphere, with most of the oxyds, acids, and neutral salts, and with many other compounds. But the more complicated combinations of nature, even in the mineral kingdom, are in general beyond our reach, and any attempt to imitate organised bodies must ever prove fruitless; their formation is a secret that rests in the bosom of the Creator. ”

“ It is difficult to determine at what point precisely it may be most eligible to enter on the history of vegetation; every part of the subject is so closely connected, and forms such an uninterrupted chain, that it is by no means easy to divide it. Had I begun with the germination of the seed, which, at first view, seems to be the most proper arrangement, I could not have explained the nature and fermentation of the seed, or have described the changes which manure must undergo, in order to yield the vegetable elements. ”

“ It is sometimes as much beyond our power to obtain a simple body in a state of perfect purity, as it is to imitate a complicated combination; for the operations by which nature separates bodies are frequently as inimitable as those which she uses for their combination. This is the case with carbon; all the efforts of chemists to separate it entirely from other substances have been fruitless, and in the purest state in which it can be obtained by art, it still retains a portion of hydrogen, and probably of some other foreign ingredients. ”

“ ON ANIMALISATION, NUTRITION, AND RESPIRATION.
MRS. B.
We have now learnt of what materials the animal system is composed, and have formed some idea of the nature of its organisation. In order to complete the subject, it remains for us to examine in what manner it is nourished and supported.
Vegetables, we have observed, obtain their nourishment from various substances, either in their elementary state, or in a very simple state of combination; as carbon, water, and salts, which they pump up from the soil; and carbonic acid and oxygen, which they absorb from the atmosphere. ”

“ If all the heat which the earth has received from the sun, since the creation had been accumulated in it, its temperature by this time would, no doubt, have been more elevated than any human being could have borne. ”

“ AS you have now acquired some elementary notions of Natural Philosophy, I am going to propose to you another branch of science, to which I am particularly anxious that you should devote a share of your attention. This is Chemistry, which is so closely connected with Natural Philosophy, that the study of the one must be incomplete without some knowledge of the other; for, it is obvious that we can derive but a very imperfect idea of bodies from the study of the general laws by which they are governed, if we remain totally ignorant of their intimate nature. ”

“ Organised bodies are such as are endowed by nature with various parts, peculiarly constructed and adapted to perform certain functions connected with life. Thus you may observe, that mineral compounds are formed by the simple effect of mechanical or chemical attraction, and may appear to some to be in a great measure the productions of chance; whilst organised bodies bear the most striking and impressive marks of design, and are eminently distinguished by that unknown principle, called life, from which the various organs derive the power of exercising their respective functions. ”

“ Now we have reason to believe that a much greater proportion of these principles than is required for such purposes remains either in an elementary state, or engaged in a less useful mode of combination in the mineral kingdom. Possessed of such immense resources as the atmosphere and the waters afford us, for oxygen, hydrogen, and carbon, so far from being in danger of working up all our simple materials, we cannot suppose that we shall ever bring agriculture to such a degree of perfection as to require the whole of what these resources could supply. ”

“ The modern chemists, instead of directing their ambition to the vain attempt of producing any of the original substances in nature, rather aim at analysing and imitating her operations, and have sometimes succeeded in forming combinations, or effecting decompositions, no instances of which occur in the chemistry of Nature. They have little reason to regret their inability to make gold, whilst, by their innumerable inventions and discoveries, they have so greatly stimulated industry and facilitated labour, as prodigiously to increase the luxuries as well as the necessaries of life. ”

“ I should not omit also to mention that bodies, in crystallising from their watery solution, always retain a small portion of water, which remains confined in the crystal in a solid form, and does not reappear unless the body loses its crystalline state. This is called the water of crystallisation. But you must observe, that whilst a body may be separated from its solution in water or caloric simply by cooling or by evaporation, an acid can be taken from a metal with which it is combined only by stronger affinities, which produce a decomposition. ”

“ Carbon forms a considerable part of the solid matter of all organised bodies; but it is most abundant in the vegetable creation, and it is chiefly obtained from wood. When the oil and water (which are other constituents of vegetable matter) are evaporated, the black, porous, brittle substance that remains, is charcoal.
CAROLINE.
But if heat be applied to the wood in order to evaporate the oil and water, will not the temperature of the charcoal be raised so as to make it burn; and if it combines with oxygen, can we any longer call it pure? ”

“ You may easily conceive, therefore, that without entering into the minute details of practical chemistry, a woman may obtain such a knowledge of the science as will not only throw an interest on the common occurrences of life, but will enlarge the sphere of her ideas, and render the contemplation of nature a source of delightful instruction. ”

“ You may perceive this effect in a sultry day, if you attentively observe the strata of air near the surface of the earth; they appear in constant agitation, for though it is true the air is itself invisible, yet the sun shining on the vapours floating in it, render them visible, like the amber dust in the water. ”

“ It is true that there at first appears to be a great analogy between radiation and reflection, as they equally convey the idea of the transmission of caloric.
But if you consider a little, you will perceive that when a body radiates caloric, the heat which it emits not only proceeds from, but has its origin in the body itself. Whilst when a body reflects caloric, it parts with none of its own caloric, but only reflects that which it receives from other bodies. ”

“ It is perhaps more easy to conceive than to express—let me consider—Is not life the power which enables both the animal and the vegetable creation to perform the various functions which nature has assigned to them? ”

“ There is indeed scarcely any mineral substance more useful to mankind than alumine. In the state of clay, it forms large strata of the earth, gives consistency to the soil of valleys, and of all low and damp spots, such as swamps and marshes. The beds of lakes, ponds, and springs, are almost entirely of clay; instead of allowing of the filtration of water, as sand does, it forms an impenetrable bottom, and by this means water is accumulated in the caverns of the earth, producing 56 those reservoirs whence springs issue, and spout out at the surface. ”

“ We have already observed that pressure is an obstacle to evaporation: there are liquids that contain so great a quantity of caloric, and whose particles consequently adhere so slightly together, that they may be rapidly converted into vapour without any elevation of temperature, merely by taking off the weight of the atmosphere. In such liquids, you perceive, it is the pressure of the atmosphere alone that connects their particles, and keeps them in a liquid state. ”