The four preceding definitions are quoted by Mr. Parkes, in his Chemical Catechism.

Dr. Johnson (from Arbuthnot) defines “chymistry” as “philosophy by fire.”

Mr. Brande says, “It is the object of chemistry to investigate all changes in the constitution of matter, whether effected by heat, mixture, or other means.”—­Manual, 3rd edit. 1830.

Dr. Ure says, “Chemistry may be defined the science which investigates the composition of material substances, and the permanent changes of constitution which their mutual actions produce.”—­Dictionary, edit. 1830.

Sir Humphry Davy, in his posthumous work,[6] says, “There is nothing more difficult than a good definition of chemistry; for it is scarcely possible to express, in a few words, the abstracted view of an infinite variety of facts.  Dr. Black has defined chemistry to be that science which treats of the changes produced in bodies by motions of their ultimate particles or atoms; but this definition is hypothetical; for the ultimate particles or atoms are mere creations of the imagination.  I will give you a definition which will have the merit of novelty, and which is probably general in its application. Chemistry relates to those operations by which the intimate nature, of bodies is changed, or by which they acquire new properties. This definition will not only apply to the effects of mixture, but to the phenomena of electricity, and, in short, to all the changes which do not merely depend upon the motion or division of masses of matter.”

Cuvier, in one of a series of lectures, delivered at Paris, in the spring of last year, says, “the name chemistry, itself, comes from the word chim, which was the ancient name of Egypt;” and he states that minerals were known to the Egyptians “not only by their external characters, but also by what we at the present day call their chemical characters.”  He also adds, that what was afterwards called the Egyptian science, the Hermetic art, the art of transmuting metals, was a mere reverie of the middle ages, utterly unknown to antiquity.  “The pretended books of Hermes are evidently supposititious, and were written by the Greeks of the lower Empire.”

Crystallization.

Why are the crystals collected in camphor bottles in druggists’ windows always most copious upon the surface exposed to the light?

Because the presence of light considerably influences the process of crystallization.  Again, if we place a solution of nitre in a room which has the light admitted only through a small hole in the window-shutter, crystals will form most abundantly upon the side of the basin exposed to the aperture through which the light enters, and often the whole mass of crystals will turn towards it.—­Brande.

Why is sugar-candy crystallized on strings, and verdigris on sticks?

Because crystallization is accelerated by introducing into the solution a nucleus, or solid body, (like the string or stick) upon which the process begins.