denfe by the desertion of moisture, each Stratum within itself had its Fiffures likewise, which for the most part being influenced by peculiar diftinct laws, were either perpendicular, horizontal, or oblique; but at the angles of different Strata, were shattered, ragged, and in all directions. "Linnæus wonders at

"the nature of that force, which split the rocks into those "cracks; but probably the caufe is very familiar; they were "formed moift, and cracked in drying." (Hill). This may account for the roughness or smoothness of the walls of fome Lodes. But whether this theory is difputable or not, we are nevertheless certain, that cracks, or Fiffures, are abundant in all parts of fubterranean matter; and likewife that those very Fiffures are the wombs or receptacles of all Metals, and most Minerals.

;

The comparative smallness of the largest Fiffures to the bulk of the whole earth, is really wonderful. In the fineft pottery can make, by a microscopick view, we may discover numerous cracks and Fiffures fo fmall, as to be impenetrable to any fluid, and impervious to the natural optick: therefore if a globe of earth, whose circumference is 24,000 miles, is only fplit into the very fmall comparative clefts we behold, how wife and good must that Creator be who hath so contrived by his laws of attraction, repulfion, and gravity, to fix and settle the limits of his creation within their juft and proper bounds! No; the great Architect, who contrived the whole, determined the feveral parts of his scheme, fo to operate, as that one useful effect fhould become the beneficial caufe of another. God provided for the uses of things in his first ideal difpofition of them and their respective beneficial ufes flowed naturally from each other, thus aptly difpofed. Hence it happens, that matter could not contract itself into folid large maffes, without leaving Fiffures between them; and yet the very Fiffures are as neceffary and useful as the Strata through which they pafs. They are the drains that carry off the redundant moisture from the earth, which, but for them, would be too full of fens and bogs for animals to live or plants to thrive on. In these Fiffures, the feveral ingredients which form Lodes, by the continual paffing of waters and the menftrua of Metals, are educed out of the adjacent Strata, collected and conveniently lodged in a narrow channel much to the advantage of those who fearch for and pursue them; for if Metals and Minerals were more difperfed, and scattered thinly in the body of the Strata, the trouble of finding and getting at Metals (thofe neceffary inftruments of art

and commerce and the ornaments of life) would be endlefs, and the expence of procuring exceed the value of the acquifition.

"These Fiffures," fays Agricola de Ortu, &c. "were the "channels through which the waters retired at the time of the "creation into the ocean, when the dry land made its first ap

pearance : e:" and Woodward in his Nat. Hift. thinks they are breaches made in the Strata by the retiring waters of the deluge, prior to which æra (according to his hypothefis) there could be neither Fiffure nor Lode. The opinion of the former is eafily refuted; for the walls of the Fiffures in fome places are too hard to be overcome, and to yield to the power of any current of water; and in other places too fair and tender to endure the force of fuch a torrent: befides, their eaft and weft direction, have not that tendency, in our parts, to discharge into the ocean, as they might seem to show, if their courses made for St. George's channel in the north, and the British channel in the fouth. With regard to the latter opinion, our Shodes will notoriously evince the mistake; as the Fiffure must be antecedent to the matter of its contents, whofe Shodes, it is generally believed, were separated from the fuperior part of the Lode by the retiring diluvium.

The infide of thofe Fiffures are commonly glidered or coated over with a hard, cryftalline, earthy fubftance or rind, which very often in breaking of hard Ore comes off with it, and is vulgarly called the Caples or Walls of the Lode: but I take it the proper walls of the Lode are the fides of the Fiffure itself, and not this coat, which is the natural plaifter upon those walls, furnished perhaps by the contents of the Fiffures, or from oozings of the environing Strata. We can presently fee the breadth of a Lode or of a branch, by the incrufted fides of the Stones of Ore, if brought whole to grafs, although we were never under-ground to take the measure of it; therefore it is common to fay, "I perceive the breadth of this or that Lode, "to be fo many inches wide; because here are the smooth "walls or caples affixed to and broke off with the Stones of "Ore." But this can be only in fmall Lodes, and hard Strata, where the Lode breaks ftoney. If a Lode is inclinable to yield any sort of Ore, it is the more promifing provided the caples or walls of the Lode are regular and fmooth, or at leaft if one of them is fo; but if they are uneven and rugged, it is the less encouraging. There are, however, but few Lodes or Fiffures that make regular walls, until they are funk on a few fathoms.

Thus,

Thus, the medullary or inner part of a Fiffure, in which the Ore lies, is all the way environed and bounded by two walls or coats of Stone, which are generally parallel to each other, and include the breadth of the vein or Lode; fo that when the Miners dig down or along in a large Lode, then the roof, i. e. the upper, the hanging wall, or incumbent wall of the Lode or Fiffure, is (in a certain proportion according to its inclination. or underlie) over their heads; and the lower, or other wall or rind, is under their feet and further, whatever angle of inclination fome Fiffures make at firft in the firm folid Strata, they feldom vary from the fame in depth: there are, however, fome exceptions to this rule. Some Fiffures are very uncertain and different in fize; for they may be very fmall near the furface, or very wide in depth, and vice verfa; but as to the regular breadth or largeness of Lodes in their length or direction, they generally make a great variation; for although a Fiffure may be many fathoms wide in one particular place, yet, a little further east or west, it may, not perhaps be an inch wide.

This variation may happen from feveral caufes, but more especially in very compact Strata, when the Lode or Fiffure is fqueezed, as it were, through means of hard rocks, which feem to comprefs and ftraiten the Fiffure. However, a true Lode, Course, or Fiffure, is never entirely cut out or destroyed by hard rocks or Strata; for the Fiffure always continues through the hardness, yielding a rib or string of metallick Ore, or else of a veiny fubftance; which often ferves for a leader for the Miners to follow, until it fometimes brings them again to a large and rich part of the impregnated Fiffure all which variety of fize in the length, breadth, and depth of Fiffures, fhews that they are the immechanical operations of nature, to fix and settle different congeries of mixed bodies into their peculiar shapes and pofitions.

As to the length and depth of Fiffures, perhaps they feldom admit of any period or limitation; for none can tell how long or how deep they reach: but in regard of their breadth, thickness, width, or largenefs, they are limited and various. Though the depth of Fiffures is unlimited beyond the power of man to follow after, yet it appears in general, that their fruitfulness for Metal

is distinct and limited. The richest state for Copper is between forty and eighty fathoms deep, and for Tin between twenty and fixty; and though a great quantity may be raised of either at

fourscore

fourfcore or one hundred fathoms, yet the quality is often decayed and dry for Metal.

The Fiffures then of Cornwall, which are productive of Metals and Minerals in their progrefs or direction, are extended eaft and weft; or, more properly fpeaking, one end or part of the Fiffure points and runs weft and by fouth, or else weft and by north, or thereabout; and the other end looks or tends eaft and by fouth, or eaft and by north and thus they often pafs through a confiderable tract of country, with little or no variation in their directions, except they are obftructed by fome intervening cause; of which hereafter, when we come to speak of the interruption of Lodes, &c. Henceforward we shall not always take notice of their deviation from the cardinal points of the compafs; but, for the most part, fhall confider them as tending eaft and weft, as the only Fiffures which are filled with Tin and Copper Ores in Cornwall.

Befides this eaft and weft direction of Fiffures, there is yet another of a contrary manner and tendency, which the Miners properly name, the underlying of the Lode, or the Hade. This is the deflection or deviation of the Fiffure from its perpendicular line, as it is followed in depth like the flope of the roof of a house, or the defcent of the fide of a fteep hill. Inftead of its tending directly downwards to the center of the earth, it inclines either to the north or the fouth, or nearly fo. Suppose, for inftance, one fide of the roof of a church to be a Lode bared of its incumbent Strata: the length of it eaft and weft, will fhew what I mean, by the direction of the Lode or Fiffure; and the flope or fide will explain its inclination or tendency downward that is, the north fide of the roof underlies north, and the fouth fide underlies fouth: fo that if a Miner fhould dig down perpendicularly where he first began, or cut the Lode, then it would foon be gone away from him, either to the north or to the fouth: therefore, when it happens thus, they are often obliged to fink new fhafts or pits on the underlie or inclination of the Lode, to cut it in depth, for the ease and conveniency of winding or drawing up the water and Ore in a perpendicular line. This underlying varies much in different Lodes, and fometimes alfo in the fame Lode; for it will often flope or underlie a small portion different ways, as hard Strata on either fide may feem to force it. Some Fiffures do not alter much from a perpendicular; and fome do underlie a fathom in a fathom; that is, for every fathom which they go down in depth, they

are

are alfo gone a fathom further to the fouth or to the north, which ever way the inclination or underlie may be. Other Fiffures, again, underlie fo faft, or obliquely, that they differ not much from an horizontal pofition, and they are thence called Flat Lodes, or Lode Plots. There is another fort of Flat Lode or Lode Plot, which underlies irregularly with refpect to other Lodes or Fiffures; for this underlies or widens horizontally for a little way, and then goes down perpendicularly not unlike ftairs, with only a fmall ftring or leader to follow after; and thus they alternately vary, and yield Ore in feveral flat or horizontal Fiffures. Yet this kind of Fiffure is very rarely met with, and is wrongly called by the Tinners, a Floor or a Squat, which properly speaking is a hole or chafm impregnated with Metal, that makes no continued line of direction, or regular walls; nor yet goes down any confiderable depth; for when a Floor of Ore of this fort is dug away, there appears no footstep or fign of a vein or Fiffure, either under foot, or pointing leading any where elfe. Alonzo Barba, in the Spanish tongue, calls it a Sombrero, which fignifies a Hat or a Heaped Mine, where Metal is found in a heap together. In Cornwall, they call it a Bunny of Ore or Tin; and fometimes "The Pride of "the Country;" which laft epithet we apprehend more properly belongs to the Bryle or loofe fhattery back of a Lode, when it is very rich for Tin or Copper, immediately to the day or furface. Inftances of Bunnys of Ore are very rare with us. We have heard of fuch among the Tin Mines in St. Juft, near the Land's End; and that there are feveral fuch chafms, impregnated with Copper or Lead, in Wales and the north of England, where they are called Pipes of Ore. In the latter we have been informed of a Pipe of Copper Ore, called Eaton Mine, which is two hundred fathoms deep, the Sough or Adit being one hundred fathoms below the furface. When thofe Pipes are exhausted, if they find water come in upon them, they work to meet it, without regarding what point of the compass it flows. from; and this oftentimes leads them to another Pipe or Bunny of Ore. Likewise, if a few Stones of Tin are found difperfed in our foft Grouan Stratum, by properly remarking the tendency of these Stones, and where the heaviest part of them points, it may be nearly gueffed how far off another little Pipe or Bunny of Ore may be; or, at least, they will bring you to what is more natural, a true Lode, as we every day experience in our discoveries of Tin Lodes by Shodeing, as will be hereafter defcribed.