Mr. Sedgwick then proceeds to argue that different gravel beds having been formed at different periods, it may happen from the nature of diluvial action, that mixtures of the materials of different beds may occur; and consequently that "in the very same deposit we may find the remains of animals which have lived during different epochs in the history of the earth." Page 33.

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He then shows how, from the double testimony of the widely existing traces of diluvial action, and the record of a general deluge contained in the sacred Scriptures, the opinion was naturally formed that all those traces were referable to one and the same action: though we ought in philosophical caution to have hesitated in adopting that opinion, because among the remnants of a former world, entombed in these ancient deposits, we have not yet found a single trace of man, or of the works of his hands." Page 34. Lastly, he strenuously denies that the facts of geological science are opposed to the sacred records, or to the reality of an historic deluge; and for himself, utterly rejects such an inference: and argues justly, that there is an accordance between the absence of human remains in these diluvial beds of gravel, and the supposed antiquity of their formation, inasmuch as the phenomena of geology, and the testimony of both sacred and profane history, "tell us in a language easily understood, though written in far different characters, that man is a recent sojourner on the surface of the earth." Page 35.

SECTION VI.
Metals.

THE atmosphere, and the vegetable, and animal kingdoms, being three out of the four general departments of the external world, are most extensively necessary to the welfare, if not to the very existence, of every individual: but even communities of men, in an uncivilized state indeed, have existed, and in

some parts of the earth are still existing, without any further aid from the mineral kingdom than that, which the common soil affords to the growth of the food which supports them. But a civilized state of society is the natural destination of man; and such a state of society is incapable of arising or being maintained, without the aid of mineral substances: and this assertion holds more particularly with respect to the metallic species.

In that department of civilized intercourse which consists in the exchange of the commodities of life, what other substance could be an equivalent substitute for gold and silver, or even copper, as a medium of that exchange? In what constant use, and of what immense importance, are some of the commonest metals in agriculture, and in the arts; or for the various purposes of domestic life! Nor have any substances more successfully exercised the powers of the mind, in the discovery or improvement of physical truths; or more largely contributed to the benefit of mankind by the practical application of those truths. We owe it to the researches of philosophy, not only that new and highly valuable metals have been discovered; but that the general value of the metals previously known, has been advanced by extended and improved applications of their inherent properties, or by the invention of new metallic combinations or alloys.

If a convincing and familiar proof of the extensive application of the metals to the common purposes of life were required, we need only refer to the case of many a common cottager, who could not carry on his daily concerns and occupations without the assistance of several of the metals. He could not, for instance, make his larger purchases, nor pay his rent, without silver, gold, and copper. Without iron he could neither dig, nor plough, nor reap; and, with respect to his habitation, there is scarcely a part of the structure itself, or of the furniture contained in it, which is not held together, to a greater or less

extent, by means of the same metal: and many articles are either entirely of iron, or of iron partially and superficially coated with tin. Zinc, and copper, and antimony, and lead, and tin, are component parts of his pewter and brazen utensils. Quicksilver is a main ingredient in the metallic coating of his humble mirror: cobalt and platina, and metals perhaps more rare and costly than these, as chrome, are employed in the glazing of his drinking cups and jugs. And if he be the possessor of a fowling-piece, which commonly he would be, arsenic must be added to the foregoing list, as an ingredient in the shot with which he charges it; for it is arsenic which enables the shot, during the process of its granulation, to acquire that delicately spherical form by which it is characterized. So that the whole number of metals made use of by society at large for common purposes, amounting to less than twenty, more than half of these are either directly used by the mere peasant, or enter into the composition of the furniture and implements employed by him.

In estimating the value of those mineral substances which were considered in the preceding chapter, as applicable to the common purposes of life, their degree of hardness is the property of principal consideration: but, in addition to this, metallic bodies possess some peculiar properties which very greatly increase their value. Thus, under a force acting perpendicularly on their surface, as under repeated blows of the hammer, or compression by rollers, many of them are capable of being expanded to a greater or less extent; some of them to such an extent as to become thinner than the thinnest paper; which property in its various degrees is expressed by the term malleability: others, though not possessing any great degree of malleability, may be drawn out into a wire, sometimes so fine as scarcely to be visible by the naked eye; which property is expressed by the term ductility. All of them are capable of being expanded or contracted in every direction by an increase or

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decrease of their temperature; the degree of this expansibility, as of its opposite effect, depending on the degree of the temperature. And lastly, in connexion with certain points of temperature, all the metals are capable of existing either in a solid or in a liquid state and their property of passing from a solid to a liquid state, in consequence of the agency of heat, is called their fusibility.

Into the detail of the different degrees in which these properties are possessed by different metals, it belongs to the chemist to enter. What we have at present to consider is, the advantage accruing to society from these properties themselves, and from their existence in that particular degree in which they actually do exist in the different metals: to show, for instance, that those metals which possess malleability in a greater ratio than ductility, or ductility in a greater ratio than malleability, are of infinitely greater value than if the converse were true: and so with respect to the property of fusibility. Thus gold, being comparatively scarce, and principally valuable on account of its colour, its resplendency, and its remarkable power of resisting the action of the air, and of various agents which readily tarnish or rust the more common metals, (all which properties reside on the mere surface,) a given quantity of such a metal is consequently more valuable in proportion to the degree of its malleability; because it may be extended over a greater surface: and no metal possesses this property in so high a degree as gold; so that, as far as the eye is the judge, the most ordinary substance may be made to represent the most costly, at a comparatively trifling expense: while in the degree of its ductility, which in gold would be, for general purposes, of little moment, it is inferior to most of the metals.*

*It should be kept in mind that this observation is applied to unalloyed or pure gold; for, when alloyed, this metal is capable of being drawn out into a comparatively fine wire. Dr. Wollas

Iron, again, is malleable to a degree which renders it most valuable as a material for fabricating all kinds of instruments for mechanical, domestic, or philosophical purposes; and it is capable of being hardened by well known processes sufficiently for the numerous and important works of the carpenter and mason, and the equally important purposes of war, agriculture, and the arts. A greater degree of malleability, in a metal employed for such purposes as those for which iron is usually employed, especially as this metal is very easily corroded by rust, would clearly have added nothing to its practical value: while its degree of ductility, which exceeds that of every other metal, combined with its capability of being hardened in various degrees, occasionally confers a value on it greatly superior to that of gold.

From the difference in the degree of fusibility of different metals, aided by the disposition which they have to unite so as to form an alloy, arises the possibility of covering one metal in a solid state with a superficial coating of another metal in a state of fusion. I am not aware that this method is employed, at least to any extent, in any other instances, than in the application of tin to the surface of copper or of iron: but, were there an hundred similar instances, they would not lessen the value of this, as affording an illustration of that principle which has been borne in mind throughout this treatise. Consider only the respective degree of abundance of each of the three metals just mentioned, and the difference in some of their qualities with respect to external agents, and we shall have ample reason for being assured that, on this as on every other occasion, we may say of the Creator of material things-"In wisdom hast Thou made them all."

ton indeed suggested a method of drawing out even pure gold into an exceedingly fine wire, by enclosing it in a mass of a highly ductile metal, drawing out the mixed metal into fine wire, and disengaging the gold from the metal in which it was enclosed, by any acid which would dissolve the latter without affecting the gold itself.