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state of perfection without a metallic alloy. The combining of alkali and sand, and certain clays and flints together, to form glass and porcelain, is a chemical process; the colours which the artist employs to frame resemblances of natural objects, or to create combinations more beautiful than ever existed in nature, are derived from chemistry;-in short, in every branch of the common and fine arts, in every department of human industry, the influence of this science is felt; and we may find in the fable of Prometheus taking the flame from heaven to animate his man of clay, an emblem of the effects of fire, in its application to chemical purposes, in creating the activity and almost the life of civil society.—Abridged from "the Last Days of a Philosopher," by the late Sir Humphry Davy.

Why may real philosophers be considered to have done much by their own inventions for the useful arts?

Because the chemical or mechanical manufacturer has merely applied what the philosopher has made known; he has merely worked upon the materials furnished to him. Thus, the chlorine, or oxymuriatic gas, of Scheele, was scarcely known, before it was applied by Berthollet to bleaching; scarcely was muriatic gas discovered by Priestley, when Guyton de Morveau used it for destroying contagion. Platinum has owed its existence, as a useful metal, entirely to the labours of an illustrious chemical philosopher; look at the beautiful yellow afforded by one of the new metals, chrome; consider the medical effects of iodine, in some of the most painful and disgusting maladies belonging to human nature, as cancer and bronchocele. We

The improvements of porcelain in this country, as well as those made in Germany and France, have been entirely the result of chemical experiments; the Dresden and the Sèvres manufactories have been the work of men of science; and it was by multiplying his chemical researches, that Wedgewood was enabled to produce, at so cheap a rate, those beautiful imitations, which, while they surpass the ancient vases in solidity and perfection of material, equal them in the elegance, variety, and tasteful arrangement of their forms.

have no history of the manner in which iron was rendered malleable; but we know that platinum could only have been worked by a person of the most refined chemical resources.- Sir H. Davy.

Why is the apparatus essential to the modern chemist much less bulky and expensive than that used by the ancients?

Because an air-pump, an electrical machine, a voltaic battery, (all upon a small scale) a blowpipe apparatus, a bellows and forge, a mercurial and water-gas apparatus, cups and basins of platinum and glass, and the common re-agents of chemistry, are all that are required. All the implements absolutely necessary, may be carried in a small trunk; and some of the best and most refined researches of modern chemists, have been made by an apparatus which might with ease be contained in a small travelling carriage, and the expense of which is only a few pounds. Chemistry is not injurious to the health; the modern chemist is not like the ancient one, who passed the greater part of his time exposed to the heat and smoke of a furnace, and the unwholesome vapours of acids and alkalies, and other menstrua, of which, for a single experiment, he consumed several pounds.- Sir H. Davy.

ATTRACTION OR AFFINITY.

Why is our earth a globe?

Because of the general attraction by which all its parts are drawn towards each other, that is, towards a common centre; by which means the mass assumes the spherical or rounded form.

We have interesting instances of roundness from the same cause in minute masses, as the particles of a mist or fog floating in air,-there, mutually attracting and coalescing into larger drops, and then forming rain-dew-drops-water trickling on a duck's wingthe tear dropping from the cheek-drops of laudanum -globules of mercury, like pure silver beads, coalescing

when near, and forming larger ones-melted lead allowed to rain down from an elevated sieve, which, by cooling as it descends, retains the form of its liquid drops, and becomes the spherical shot-lead of the sportsman.-Arnott.

Why is the prescription of medicine by drops an unsafe method?

Because, not only do drops of fluid from the same vessel, and often of the same fluid of different vessels, differ in size, but also drops of the same fluid, to the extent of a third, from different parts of the lip of the same vessel.

Why has it been said that the whole world, if the atoms could be brought into absolute contact, might be compress

ed into a nutshell?

Because of the exceedingly little of really solid matter even in the densest mass, as evident in the noncontact of atoms, even in the most solid parts of bodies; from the very great space obviously occupied by pores; the mass often having no more solidity than a heap of empty boxes, of which the apparently solid parts may still be as porous in a second degree, and so on; and from the great readiness with which light passes in all directions through dense bodies, like glass, rock crystal, diamond, &c. We have as yet no means of ascertaining exactly what relation this idea has to truth.-Arnott.

Why may the doctrine of ultimate atoms be considered as established?

Because, according to the late Dr. Wollaston, the earth's atmosphere is limited, and consequently matter has a finite divisibility. "Yet," observes another, “of the smallest atom we can always imagine the half."

Why is the density, or the quantity of atoms which exist in a given space, very different in different bodies?

Because of three different circumstances: first, of the size or weight of the individual atoms; secondly,

on the degree of porosity just now explained; thirdly, on the proximity of the atoms in the more solid parts, which stand between the pores. As an example of the different degrees of density, a cubic inch of lead is 40 times heavier than the same bulk of cork.—Arnott. Why are certain bodies solid?

Because their parts cohere so firmly as to resist impression.

Lavoisier has explained solidity thus:-"The particles of all bodies may be considered as subject to the action of two opposite powers, repulsion and attraction, between which they remain in equilibrio. So long as the attractive force remains stronger, the body must continue in a state of solidity; but if, on the contrary, heat has so far removed these particles from each other, as to place them beyond the sphere of attraction, they lose the cohesion which they before had with each other, and the body ceases to be solid. "

Why do blue and yellow powders, when mixed, form a green powder?

Because of the mere effect arising in the eye from the intimate mixture of the yellow and blue light separately and independently, reflected from the minute particles of each; and the proof is had by examining the mixture with a microscope, when the yellow and blue grains will be seen separately and quite unaltered. -J.F. W. Herschel.

Why cannot a similar separation be detected in liquid green?

Because of the excessive minuteness of the parts, and their perfect intermixture, by agitating the blue and yellow liquids together. From the mixture of two powders, extreme patience would enable any one, by picking out with a magnifier grain after grain, to separate the ingredients. But when liquids are mixed, no mechanical separation is any longer practicable: the particles are all so minute as to elude all search. -J.F. W. Herschel.

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walls, it is full of air, just as an open vessel, immersed in the sea, is full of water; and if air were not allowed to escape from it, even so small a body as an apple could not be pressed into it additionally by less force than fifty or sixty pounds.

Why is heat produced on slacking quick-lime?

Because of the violence of the chemical action, and the solidification of the water. In this process 68 parts of lime solidify 32 parts of water; but it is remarkable, that in making what we call lime-water, 500 parts of water are required to dissolve one part of lime.

Why is it a vulgar error to say quick-lime, or oil of vitriol, burns?

Because they powerfully corrode animal and vegetable substances, and become violently hot from their combination with water. "They are, therefore, set down in vulgar parlance, as substances of a hot nature; whereas, in their relations to the physical cause of heat, they agree with the generality of bodies similarly constituted." They owe the sensation of heat which they excite, to chemical stimulants, and not at all to their being actually hot.

Why are not bitter and sweet essential qualities of matter?

Because, as Dr. W. Herschel has recently discovered, the mixing of nitrate of silver with hypo-sulphate of soda, both remarkably bitter substances, produces the sweetest substance known. Thus, bitter and sweet, as well as sour, appear not to be an essential quality in the matter itself, but to depend on the proportions of the mixture which composes it.

CRYSTALLIZATION.

Why do the figures of crystals vary in regularity? Because their regularity is influenced by the rapidity of the evaporation: thus, if the process be slowly conducted, the particles unite with great regularity;

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