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FOR THE PORT FOLIO.

INTRODUCTORY LECTURE ON MINERALOGY.

BY THOMAS COOPER, M. D.

We are indebted to our friend, professor Cooper, for a copy of his interesting lecture, introductory to a course, which he proposes to deliver in the university of Pennsylvania, on an important branch of natural history. Theophrastus, among the Greeks, and Pliny, among the Latins, have treated this subject very superficially; Avicenna, in the tenth century, wrote a perspicuous treatise, in which he made the same division of minerals into four classes which is still observed; but he added little to what we had already learned from Pliny. In the sixteenth century, George Agricola, a Saxon, furnished ample historical details respecting the art of mining, and, in a German translation of the new Latin words which he was obliged to coin, in order to express substances, unknown to the ancients, he has left a very valuable vocabulary. In more modern times, the greatest part of Germany, Hungary, and Poland have been described: Norway has been partly travelled through. That indefatigable lover of science, the baron Humboldt, has given a most interesting account of Mexico and great part of South America. Different portions of Italy, Switzerland, and France, have also been examined; and a valuable account has been published, by Cuvier and Brogniart, of the structure of the environs of Paris. Much curious and useful information has resulted from the labours of professor Jameson and his pupils, and several facts have been brought to light by colonel Imrie, on the mineralogy of Great Britain. Mr. Cooper does justice to the merits of colonel Gibbs, Mr. McClure, and professor Cleaveland, in our own country, and we rejoice that the gentlemen to whom the government of our university is entrusted, have secured to us the various learning, the useful knowledge, and the fruiful resources of the present lecturer. The advantages arising from the co-operation of such a mind, in this institution, are incalculable. His loss would be a public injury.

We live upon the surface of a globe of about eight thousand miles in diameter; whose surface alone seems destined to be the habitation of living

and organized beings. We have pierced into that surface about one thousand yards; not quite so deep as the thin yellow rind of an orange, compared to its remaining bulk. Still, trifling as this shallow surface appears to be, it is of more importance to us than all the rest; for it is our all. For what other purposes the unfathomable depths of the earth's diameter have been created by the Divine Being, that Being who created them, alone can know: it is enough for us, that we are permitted to investigate as much of that surface, as is necessary to our existence, or can add to our enjoyments. Satisfied with the portion which Divine Wisdom has assigned to us, let us convert that portion to the purposes it was destined to fill, so far as we are connected with it in the scale of creation.

What then are the substances we trample upon? What are those we dig up? What are their properties? What good use can we make of them? By what appropriate nomenclature can we distinguish them? The answers to these questions, comprising by far the largest portion of really useful knowledge, are furnished by the modern science of mineralogy. It is a modern science: for although the study of mineral substances, be coeval with the days of Democritus of Abdera, of Aristotle, of Theophrastus and Dioscorides, it has been pursued with a prospect of practical utility, only within the last thirty years.

In examining the surface of our globe, and the substances through which we pierce in digging for metals-and in considering the appearances that mountains, valleys, and ravines present to our contemplation in their natural state-we find, that there are a series of strata super-imposed one on the other, which, to a certain degree, have the appearance of regularity in their arrangement, and order of succession in the various countries where they have been observed: but with apparent anomalies in this respect, which repeated observations promise hereafter to explain, we find that these strata are more or less extensive-that they are usually accompanied in all countries by similar deposits under similar circumstancesthat they contain various substances imbedded in them; some common, some peculiar to each series of depositions-that certain metals and minerals are found in some strata, and seldom or never in others-that some of them are so situated as to form a dip or an angle with the horizon, of various degrees of obliquity-that others are horizontal, or nearly so that some take their figure conformably to the stratum underneath them-that others affect their own place and situation without reference to the strata above or below them that certain organic remains of animal and vegetable substances are found in some strata which are not found in others--and in short, that each of the series of strata or depositions have characters peculiar to themselves, which those who are in search of metals, coals, salt, gypsum,

limestone, and other mineral substances that are converted, or convertible to the use of man, should make themselves acquainted with, in order to conduct their search with a reasonable prospect of success. These characters of strata, form the subject of the infant science of geology.

Moreover, as no substance can be made subservient to the use or comfort of the civilized portion of the human race, but in proportion as its properties are investigated and made known, all science consists in searching out and ascertaining the properties of the substances that surround us, in order that we may discover at the same time which of those properties we can call into play, as our wants and necessities may require. The great means of ascertaining the properties of mineral substances in particular, we derive from chemistry; whose importance or rather whose indispensible necessity becomes daily more and more manifest. But we cannot always carry in our pocket, a portable laboratory. We must often wait till we can carry home the substances whose properties we are desirous of investigating, and submit to the tedious, though satisfactory, process of chemical analysis, to remove our doubts and strengthen our conjectures.

It has been found, that the external physiognomy-the features of a mineral-those characters that the eye, the ear, the smell, the taste, the touch, can ascertain-are, to a certain degree, indeed in a very high degree, connected with the more recondite properties which the chemist alone can discover by the analytical researches of his art: so that, being made acquainted with the external appearances usually assumed by bodies possessed of similar chemical properties, we can predict with some certainty the latter from the former; and convert the science of mineralogy into the short-hand of chemistry. Thus, we know by chemical analysis, the composition of the substance called gypsum, or plaster, as it is commonly called in this country: we know that it is a neutral salt, formed by the union in saturating proportions, of the acid of sulphur with the earth called lime: that it is a substance highly useful in building, in stucco work, in cementing the burrs for millstones, in making casts of statues; and, still more than all the rest, in agriculture, forming at present the cheapest of all stimulating manures, when it can be procured within a reasonable distance of the spot where it is to be employed. No one however, can discover the lime in this mineral, or the sulphuric acid in it, unless by subjecting it to the operations of the chemist. But its chemical component parts once known, they can always be affirmed with certainty of a mineral that has the external characters, the specific gravity, the degree of hardness, tenacity, insolubility, and other marks of this mineral described by the mineralogist, however different in appearance its form may seem, to one unacquainted with the

science of mineralogy: so that, of a number of stones presented to him, he will seldom be at a loss in picking out from among them the substance called gypsum. The same may be affirmed of the substances called limestone, barytes, soapstone, &c. whose external characters, with the aid of a blowpipe, a common penknife, a piece of steel, and a small vial of acid easily carried in the pocket, and which greatly facilitate mineralogical inquiries, cau in almost every instance be satisfactorily ascertained. I do not mean to assert that we shall in no case find room for doubt and hesitation; for the science of mineralogy is yet but a few years old: but in proportion as it becomes cultivated, what has happened will continue to happen; difficulties will vanish, doubts will be removed, characters will be ascertained, the nomenclature fixed, and our attention will be repaid amply by the acquisition of knowledge, equally certain and useful.

In like manner the science of geology, from the number of its votaries, is in a state of gradually progressing improvement, so that ere long, when in travelling we enter upon a country, we shall be able to form a reasonable conjecture of the minerals we may, and of those we may not expect to meet with in the district we pass over. Time will no longer be thrown away in expensive searches for that which a geologist at a glance can say, is not to be found; and the mineral riches of a country, will be ascertained with a facility that no one unacquainted with the kind of knowledge in question, can have any true conception of, imperfect as the science of geology yet is.

How many strange mistakes does the ignorance of mineralogy and geology lead those into, who know nothing of their elements! In mistaking pyrites for gold, mica for silver, quartz før diamond, ore for earth, earth for ore-in digging for coals in primitive formations, in searching for metals in strata where they have never been found! How little can be known of mining without the aid of these sister sciences! How many noble edifices are now in a state of decay, though recently erected, for want of some mineralogical knowledge in the architect! In Great Britain and in France, the cases are numerous which illustrate this remark.

Indeed, to instance in lighter matters, how easily can a mineralogist in looking at the trinkets of a modern jeweller's shop, separate the false topazes, amethysts, cornelians, agates, and onyxes from the true ones? How difficult is it for a person unacquainted with the examination of minerals, to distinguish a brilliant cut paste from a real gem, a bandeau of glass from one of diamonds? or to ascertain, without some slight aid from the chemist, the value of the precious metal, so called, in which they are set?

Whether, therefore, we recur to objects of indispensible and extensive utility, or to substances of mere ornament, something of mineralogi

cal knowledge is absolutely necessary, to enable us to pronounce with accuracy and precision, on whatever has a mineral origin.

I have already mentioned, that some attention was paid by the ancients to the objects of mineralogy; but it was a long time before the most obvious classification became prevalent:-before earths and stones, ores and metals, saline and inflammable substances were distinguished from each other.

The first scientific mineralogist was a miner of Saxony, George Agricola. He first dwelt on the external characters of minerals; distinguished, named, and described them. He was followed by several other German mineralogists between his time and the commencemant of the eighteenth century. During this period, there were but two or three English writers of character: Johnson, who published in 1667 his notitia Regni mineralis, Pryer, who wrote on the Mineralogy of Cornwall, and Dr. Woodward, who made a large collection of promiscuous minerals, and published a catalogue of them. His minerals deposited at Oxford, are still considered of great use and value, on account of the accuracy with which the localities are given.

Becher, the chemist to whom England is indebted for the practice of smelting with the coak of coals, not even yet introduced among us, so slowly is the march even of useful innovation, published his Physica Subteranea in 1708, and was the first who introduced chemistry into the science of mineralogy; proposing to describe minerals and class them, by their component parts; a practice, which every mineralogist, even at the present day, is compelled to a certain degree to pursue. For, although minerals may, in great part, be separated into families, dependant upon similarity of external character, there is no avoiding the introduction of their chemical composition; because, that not only forms the most obvious and prominent part of the scientific description which we find it convenient to give of them, but in nine cases out of ten, their uses depend on their chemical composition alone. Many writers on the continent of Europe now began to pay attention to the subject of mineralogy: but no tolerable classification was struck out till Cramer, whose chemical writings are still held in deserved reputation, divided them into metals, semi-metals, salts, inflammables, stones, earths, and waters. This was in 1739.

Linnæus, the great master of classification in modern days, subjected mineral substances as well as vegetables to classes and orders; but he was unequal to the subject, for want of practical knowledge of mineral sub

stances.

Mineralogical chemistry was greatly promoted about this time, 1736 to 1740, by Pott and Henckel, whose application of chemistry to the ana