Obs. In Art. 127 and 128, are described the transforma, tions of insects, from the egg to the worm-the worm to the chrysalis--and the chrysalis to the butterfly. The following cut represents those four states in the common catterpillar. THE EGGS, THE CATERPILLAR, CHRYSALIS, AND BUTTERFLY. XXI. Chemistry.. 515. By Chemistry we ascertain the ingredients, component parts, or first principles of which all kinds of matter are composed. DEFINITIONS. 1. Decomposition implies the separation of the elementar substances of which any compound substance is formed. 2. Pulverization signifies the mere mechanical separation of bodies into smaller ones, without being decomposed into its elementary ingredients. 3. Chemical affinity affords proof that atoms are compounded in different forms, which coalesce and dovetail together with more or less facility. 4. The sensible atoms appear attracted or repelled accordingly as they, or those of the media in which they are placed, are more or less mutually affected. 5. The substance which decomposes another, is called a chemical test or re-agent. 6. If a salt be dissolved in water, it is said to be in solution, and the water is called the menstruum. 7. When water will dissolve no more of any substance, the water is said to be saturated. 8. If we would extract the salt, we must evaporate the water by heat, with a still, a retort or alembic; and if the va por from either of these pass through a spiral tube or worm, to the receiver, we shall have distilled water: and the salt will remain in the still 9. Solid substances are reduced into powders by trituration, pulverization, and levigation; brittle substances are pulverized by hammers, pestles and mortars, stones and mullers. 10. The separation of the finer parts of bodies from the coarser is performed by means of sifting or washing 11. Filtration is a finer species of sifting, performed through the pores of paper, flannel, fine linen, sand, &c. It is employed only for separating fluids from solids. 12. Fusion, or the melting of a solid body, by the action of heat, requires, according to their several natures, crucibles of different kinds strong enough to resist the fire; made of earthenware, porcelain, or a mixture of clay and powder of black-lead, or black-lead altogether. 13. Sometimes crucibles have covers made of earthenware, but in other cases the fused metal must be exposed to a current of air: for this purpose the crucibles are broad and shallow, and are called cupels. 14. Blow pipes are used for directing the flame of a candle or lamp against any piece of ore or other substance required to be examined: and when oxygen or hydrogen gas is used instead of common air, the heat is most powerful. 15. The various degrees of heat, or atomic motion which are required for the performance of chemical operations, render it necessary that the chemist should alo be possessed of a furnace. 16. Chemical combinations are more generally influenced by the agency of powers, called by the names of attraction and repulsion, but in truth consisting of various susceptibilities of motion in the atoms of bodies, and in the columns of the media in which they are placed. 17. When a new substance is produced from the combina. tions of two others, the operation is called synthesis. When that substance is decomposed, or resolved into its constituents by the assistance of other chemical agents, the operation is termed analysis. 18. Elementary bodies are those which no art of modern chemistry has been able to decompose into other elements. 19. Atomic motion produced by percussion, by friction, or by transfer, is the cause of all the varieties of heat, fire and caloric. 20. Temperature signifies the varied intensity or violence of intestine atomic motion, which, by increasing the distance of the particles or atoms increases the volume of bodies. 21. Different bodies change their states at very different temperatures or degrees of atomic motion. Thus mercury, which becomes solid at about 40 degrees below 0 in Farenheit, boils at about 660 degrees: sulphur, which becomes fluid at 218 degrees, boils at 579 degrees; ether boils at 92 degrees. 22. Resistance, says Sir Richard Phillips, is a phenomenon of parting with received motion. A body said to be resisted, is merely parting with its motion to the atoms which it encounters in the media within which it moves; and, as it continues to part with its motion to the radiating atoms, its gradually diminished energy of motion is, in vulgar language, said to be destroyed by resistance. 23. Friction, says he, like resistance, is a mere phenomenon of parting with motion, but to a fixed body instead of a fluid and being a variation of percussion, or of transfer of motion without change of place, it produces similar phenomena of intestine atomic motion or heat, which when continued or accelerated, produces all the other phenomena of accelerated atomic motion or heat. 24. Crystallization, he says, is a mere effect of parting with atomic motion, in certain connections with, or relation to, the atoms of the surrounding media, in which the crystallized body is placed. 25. The following principles should be remembered. 1. That all fluids are combinations of heat (or transferred motion), with various substances; 2. That combustion arises from the action of heat, or motion on the parts of the combustible body: and that the process called burning, is nothing more than the oxygen df the atmosphere uniting with certain parts of the body; 3. That oxygen seems to be the acidifying principle: and that all acids are combinations of oxygen with other sub stances; 4. And that all salts are combination of an acid with other substances, called the base of the salt. Obs.-Sir Humphrey Davy, in the preliminary observations to his Elements to Chemistry, beautifully observes, that "the forms and appearances of the beings and substances of the external world are almost infinitely various, and they are in a state of continued alteration. The whole surface of the earth even undergoes modifications. Acted on by moisture and air, it affords the food of plants: an immense number of vegetable productions arise from apparently the same materials: these become the substance of animals: one species of animal matter is converted into another: the most perfect and beautiful of the forms of organized life ultimately decay, and are resolved into inorganic aggregates: and the same elementary substances, differently arranged, are contained in the inert soil, or bloom, and emit fragrance in the flower or become in animal, the active organs of mind and inelligence. In artificial operations, changes of the same order occur: substances having the characters of earth, are converted into metals; clays and sands are united, so as to become porcelain; earths and alkalies are combined into glass; acrid and corrosive bodies are formed from tasteless substances; colours are fixed upon stuffs, or changed, or made to disappear; and the productions of the mineral, vegetable, and animal kingdoms, are converted into new forms, and made subservient to the purposes of civilized life. To trace, in detail, these diversified and complicated phænomena, to arrange them, and deduce general laws from their analogies, is the business of Chemistry." 516. The ancients conceived that there were but four elements, or first principles-Air, Water, Earth, and Fire. The moderns have analyzed these four elements, and have discovered other elements of those elements, viz. Oxygen, Hydrogen, Nitrogen, Chlorine, Carbon, Caloric, (or atomic motion) Sulphur, Phosphorus, nine Earths, and twenty-eight Metals. Obs. 1.-Atmospheric AIR is now found to be a compound of Nitrogen or Asole; and Oxygen; which are preserved in a gaseous state by Caloric. WATER is found to be a compound of Oxygen and Hydrogen. EARTH is a compound of nine different substances, now called Earths. (See 526.) And FIRE is found to consist of mere atomic motion. 2.-The forms of matter are well arranged into three distinct classes, by SIR H. DAVY. The first class consists of solids; which compose the great known part of the globe. Solid bodies, when in small masses, retain whatever mechanical form is given to them: their parts are separated with difficulty, and cannot readily be made to unite after separation; some solid bodies yield to pressure, and do not recover their former figure when the compressing force is removed, and these are called non-elastic solids; others, that regain this form, are called elastic bodies. Solids differ in degrees of hardness; in colour; in degrees of opacity or transparency; in density, or in the weight afforded by equal volumes; and |