_Proficients_, those who have made great progress in any art or science. By whom was it revived? After having long lain buried, the famous Roger Bacon revived it; and from his time to the present day it has gradually progressed to a state of perfection. In former times, the art of chemistry consisted only in the knowledge of working metals, &c.; but in latter ages, its bounds have been greatly enlarged. The knowledge of Chemistry leads to many interesting and important discoveries, and the arts and manufactures are greatly indebted to its aid; indeed, it is requisite to be a good chemist, in order to attain to perfection in many of them. _Requisite_, necessary. By what other name has Chemistry been known? It was sometimes called _Alchemy_; by which is properly understood a refined and mysterious species of chemistry, formerly much practised. What were its objects? The discovery of the art of converting metals into gold, including the search after the "Philosopher's Stone," by which this change was to be effected; and the discovery of a panacea or medicine for the cure of all diseases. What was the Philosopher's Stone? A substance, for numbers of years eagerly sought for, which was to convert metals, such as lead, copper, &c. into gold. This unknown substance was called the Philosopher's Stone, probably on account of the number of learned men who engaged in the search after it. [Illustration: UNITED STATES SIGNAL STATION, PIKE'S PEAK, COLORADO.] Was this search successful? No; but the delusion lasted several centuries, notwithstanding the failures, losses, and disappointments of those engaged in it. Indeed, so severe and ruinous were these, in many instances, that laws were passed to forbid the study. In Germany, many of the alchemists who had the unfortunate reputation of possessing this wonderful stone were imprisoned and furnished with apparatus till they should purchase their liberty by making an ounce of gold. _Delusion_, an error arising from false views. _Apparatus_, a complete set of instruments or tools, by which anything is made, or any operation performed. Was any gold ever produced by this method? Not a particle; the story of a stone having the property of converting the baser metals into gold being merely an absurd fable: yet, although the pursuits of Alchemy were the most preposterous that can be conceived, the ardor with which they were followed, and the amazing number of experiments made in consequence, led to the discovery of many facts to which Chemistry is highly indebted. _Preposterous_, absurd, foolish; contrary to nature or reason. You inform me that Chemistry enables us to discover the properties of bodies by means of _analysis_ and _combination_: what do these terms imply?