*

its indestructibility and its antiseptic qualities. The other peculiar and surprising properties of charcoal were reserved for the discoveries of the present age; for these we are most especially indebted to the labours and genius of Black,*. Priestley, Cavendish, Lavoisier, Guyton, Tennant, and Berthollet, and to the gradual developement of the present improved system of chemistry.

What reflections naturally present themselves on • the consideration of the various properties of charcoal and the other simple combustibles?

This subject, when considered in all its connexions, is calculated to produce the most profound admiration; and serves to convince us of the unbounded comprehension of that Divine mind, which, in the act of creation, could foresee

* In the year 1755 Dr. Black discovered the acid gas which is thrown off from fermented liquors and from mild calcareous earth. He called it fixed air.

Dr. Priestley explained the effect of charcoal in decomposing nitrous acid, examined the gas that is thrown off in this decomposition, and pointed out the necessity of distinguishing the different gases from common air; for which the Royal Society awarded him an honorary prize.

In the years 1766 and 1767 Mr. Cavendish published papers in the Philosophical Transactions on the nature of elastic fluids, in which he announced that he had produced fixed air by the burning of charcoal. This assurance called the attention of all chemists to that surprising substance, and was the forerunner of the many discoveries which have since been made respecting its properties, &c.

Lavoisier pointed out the nature of the action of charcoal in reducing metallic oxides; investigated the nature of the combustion of the diamond; announced the exact quantity of carbon in carbonic acid; and the production of carbonic acid by the decomposition of water with ignited charcoal.

and appoint such important effects to result from the combinations and changes of the most inodorous and insipid substances. We also learn, that all the works of the Creator are perfect; and perceive with astonishment, that they are composed of elements which are in themselves incapable of destruction.*

* See Additional Notes, No. 25 and 37.

CHAPTER X.

OF METALS.

WHAT are the characteristics of the metals? The general characters of the metals are, hardness, tenacity, lustre, opacity, fusibility, malleability, and ductility but some metals are neither malleable nor ductile.*

How are the metals procured?

They are generally taken from the bowels of the earth,† in a state of combination either with other metals, with sulphur, oxygen, or with

*In the former editions of this work "great specific gravity" was mentioned as one of the characteristics of the metals; but as metallic substances have lately been discovered by Sir Humphry Davy, which have specific gravities less than that of water, this character could no longer be given to that class of bodies.

Metals are generally found in mountainous countries, in such as form a continued chain; but the metallic part of a mountain usually bears but a small proportion to its whole contents. Granite rocks seldom contain any metallic ores.

It is deserving of notice, that if minerals had been placed on the surface of the globe, they would have occupied the greatest part of the earth, and would have prevented its cultivation. Their being deposited below is a proof of management and design worthy of that Being who could furnish so great a variety of this class of bodies.

When metals are found combined with other metals they are called native alloys.

A table of the orders and the genera of the ores of metals may be seen in Dr. Thomson's Chemistry, vol. iv. 19.

acids; though a few of them have occasionally been found in a state of purity.f

*

By what methods are the metals purified from these substances?

The metals are purified from their ores by various means; such as washing, roasting, fusion, &c.; but the method must always be regulated by the nature of the ore to be assayed.§

How many metals are there?

There are twenty-seven distinct metals, which possess properties very different and distinct from cach other. I

*The sulphuric, muriatic, phosphoric, and carbonic acids are those which are generally found in combination with metals.

† Among those metals which most frequently occur in the metallic state may be ranked quicksilver. In Bishop Watson's Chemical Essays mention is made of such a mine in this country, viz. at Berwick in Northumberland, in the midst of that town; and Mr. Hume, a native of that place, assures me that he was an eye witness to this fact.

The analysis of metallic ore in the great, is always performed by fire, and this is called the dry way; but the more accurate analysis is effected by means of various chemical reagents which modern chemistry has applied to that purpose, and is termed the moist way. Before the time of Bergman every kind of analysis of minerals was conducted by fire: he was the first chemist who resorted to the method of solution in acids, which is easy, simple, and effectual.

Those who wish to investigate this subject may find ample information in Schlutter's work on mineralogy; in Henkel's Pyritologia; in Cramer on Metals; in Kirwan's Mineralogy; and in Klaproth's Essays.. Some general ideas on the subject may be collected from a well written paper of Dr. Thomson's in the second edition of his System of Chemistry, vol. iv. 174.

The several metalloids of Davy are not included in this enumeration: it will be necessary to know more of their respective properties before we can class them with the metals.

For a knowledge of most of the metals, we are indebted to the more perfect modes of analysis which modern chemistry has afforded. The ancients were acquainted with only seven of

How are the metals classed by modern chemists?

They are divided into two classes. The one contains the malleable, the other the brittle metals. This last class is sometimes subdivided into two others, viz. those which are easily, and those which are difficultly fused.

How many malleable metals are there?

Ten;* viz.

1. Gold,t

2. Platina,

6. Iron,

3. Silver,
4. Mercury,
5. Copper,

7. Tin,
8, Lead,

9. Nickel, 10. Zinc.

these metals. The properties of these were tolerably well known to the early chemists, who acquired their knowledge from the alchymists. These infatuated people tortured silver, mercury, copper, iron, tin, and lead, in every way they could devise, in order to convert them into gold. Alchymy was probably introduced into Europe by the crusaders, whose minds were prepared for the reception of any delusion. In all likelihood they picked up the idea of the transmutation of metals on their return from Palestine; and as error generally operates more powerfully than truth with such fanatics, they deluged their native country with these absurdities. The vain and conceited Paracelsus, a Swiss physician, was one of the last of the alchymists. He an-, nounced to the world that he had discovered a medicine, which would render man immortal: but worn out by his debaucheries and excesses, he gave the lie to this assertion; for he himself died, in the year 1534, at the age of 41.

In the reign of Henry IV. an act was passed to make it felony to transmute metals. This act was repealed in consequence of the suggestions of Mr. Boyle, who was aware of its absurdity.

* In this enumeration I have purposely omitted palladium, rhodium, iridium, and osmium, the four metals found in the ore of platina, as they occur in small quantities, and their properties have not yet been sufficiently examined, and it is possible that they may be merely alloys of other metals. What is known respecting them, may be seen in vol. iii. of Murray's System of Chemistry, p. 160 to 197.

+ Of these metals, the three first have been called noble or