Mine. a very bad appearance at firft, do nevertheless turn out extremely well afterwards; while others, which in the beginning feemed very rich, turn gradually worse and worfe : but in general, where a vein has a bad ap pearance at firft, it will be imprudent to be at much expence with it. times quite reverfed, and changed into perpendicular. Veins of metal, as has been already obferved, are fre When two metallic veins in the neighbourhood of each other run in an oblique direction, and of confe quence meet together, they commonly produce a body of ore at the place where they interfect; and if both are rich, the quantity will be confiderable; ut if one be poor and the other rich, then both are either en riched or impoverished by the meeting. After fome time they feparate again, and each will continue its former direction near to the other; but fometimes, though rarely, they continue united. It is a fign of a poor vein when it separates or diverges into frings; but, on the contrary, when feveral of them are found running into one, it is accounted a promifing fign. Sometimes there are branches with out the walls of the vein in the adjacent ftrata, which often come either obliquely or tranfverfely into it. If these branches are impregnated with ore, or if they underlie faster than the true vein, that is, if they dip deeper into the ground, then they are faid to overtake or come into the lode, and to enrich it; or if they do not, then they are faid to go off from it, and to impoverish it. But neither thefe nor any other marks either of the richnefs or poverty of a mine are to be entirely depended upon : for many mines, which have N° 221. other matter; and the method of recovering their vein is to drive on their work in the direction of the former part, so that their new work fhall make the fame angle with the clay that the other part of the vein does. Sometimes they fink a fhaft down from the furface; but it is generally a matter of difficulty to re cover a vein when thus loft. The method of difcovering mines is a matter of fo much difficulty, that it feems furprising how those who were totally unacquainted with the nature of metals first came to think of digging them out of the earth. According to Lucretius, the difcovery was made by the conflagration of certain woods, which melted the veins of metal in the earth beneath them; but this feems to be rather improbable. Ariftotle, however, is of the fame opinion with Lucretius, and tells us, that fome shepherds in Spain having fet fire to the woods, the earth was thus heated to fuch a degree, that the filver near the furface of it melted and flowed into a mafs; and that in a fhort time the metallic mafs was difcovered by the rending of the earth in the time of an earthquake: and the fame ftory is told by Strabo, who afcribes the discovery of the mines of Andalulia to this accident. Cadmus is faid by fome to have been the first who discovered gold: while others afcribe this to Thoas the Thracian, to Mercury the fun of Jupiter, or to Pifus king of Mine. cians, who pretended to difcover mines by inchantment. No mention is made of it, however, before the 11th century, fince which time it has been in frequent ufe; and the Corpufcular Philosophy has even been called in to account for it. But before we pretend to account for phenomena so very extraordinary as thofe reported of the virgula divinatoria, it is neceffary, in the firft place, to determine whether or not they exift. Mr Price, as has been already hinted, believes in it, though he owns that by reafon of his conftitution of mind and body he is almoft incapable of co-operating with its influence. The following account, however, he gives from Mr William Cookworthy of Plymouth, a gentleman of known veracity and great chemical abilities. Mine. of Italy; who having left his own country, went into Egypt, where he was elected king after the death of Mizraim the fon of Ham; and, on account of his difcovery, was called the Golden God. Others fay, that Eaclis or Ceacus the son of Jupiter, or Sol the fon of Oceanus, was the firft difcoverer; but Æfchylus attributes the discovery not only of gold, but of all other metals, to Prometheus. The brafs and copper mines in Cyprus were firft difcovered by Cinyra the fon of Agryopa; and Hefiod afcribes the difcovery of the iron mines of Crete to the Cretan Dactyli Idæi. The extraction of lead or tin from its ore in the island of Caffiteris, according to feveral ancient authors, was difcovered by Midacritus.-The fcripture, however, afcribes the invention of brafs and iron, or at least of the methods of working them, to Tubal Cain before the flood. Ation. In more modern times, we know that mines have been frequently discovered by accident; as in fea-cliffs, among broken craggy rocks, by the washing of the tides or floods, alfo by irrruptions and torrents of water iffuing out of hills and mountains, and fometimes by the wearing of high roads. Mr Price mentions another way by which mines have been discovered, viz. by fiery corufcations; which, he fays, he has heard from perfons whofe veracity he is unwilling to que"The tinners (fays he) generally compare thefe effluvia to blazing ftars or other whimfical like neffes, as their fears or hopes fuggeft; and fearch with uncommon eagerness the ground over which these jack-a-lanterns have appeared and pointed out. We have heard but little of thefe phenomena for many years; whether it be, that the prefent age is lefs credulous than the foregoing, or that the ground, being more perforated by innumerable new pits funk every year, fome of which, by the ftannary laws, are prevented from being filled up, has given these vapours a more gradual vent, it is not neceffary to inquire, as the fact itself is not generally believed." Mines, however, are now moft commonly discovered by investigating the nature of fuch veins, ores, and ftones, as may feem moft likely to turn to account: but there is a particular fagacity, or habit of judging from particular figns, which can be acquired only by long practice. Mines, efpecially thofe of copper, may alfo be difcovered by the harfh and difagreeable tafte of the waters which iffue from them; though it is probable that this only happens when the ore lies above the level of the water which breaks out; for it does not feem likely that the tafte of the ore could afcend, unless we were to fuppofe a pond or lake of water ftanding above it. The prefence of copper in any wa ter is eafily discovered by immerging in it a bit of polished iron, which will thus inftantly be turned of a copper colour, by reafon of the precipitation of the metal upon it. A candle, or piece of tallow put into water of this kind, will in a fhort time be tinged of a green colour. Another and ftill more remarkable method of dif covering mines is faid to be by the virgula divinatoria, or "divining rod;" which, however incredible the ftories related concerning it may be, is ftill relied on by fome, and among others by Mr Price. It is not known who was the inventor of this method; but Agricola fuppofes that it took its rife from the magiVOL. XII. Part 1. He had the first information concerning this rod from one Captain Ribeira, who deferted from the Spanish service in Queen Anne's reign, and became captain-commandant in the garrifon of Plymouth; in which town he fatisfied feveral intelligent perfons of the virtues of the rod, by many experiments on pieces of metal hid in the earth, and by an actual discovery of a copper mine near Oakhampton, which was wrought for fome years. This captain very readily fhowed the method of ufing the rod in general, but would not by any means difcover the fecret of diftinguishing the different metals by it; though, by a conftant attention to his practice, Mr Cookworthy difcovered it. Cap. tain Ribeira was of opinion, that the only proper rods for this purpose were thofe cut from the nut or fruittrees; and that the virtue was confined to certain perfons, and thofe, comparatively fpeaking, but few: but Mr Price fays, that the virtue refides in all perfons and in all rods under certain circumftances. "The rod (fays he) is attracted by all the metals, by coals, limeftone, and fprings of water, in the following order: 1. Gold; 2. Copper; 3. Iron; 4. Silver; 5. Tin; 6. Lead; 7. Coals; 8. Limestone and springs of water. One method of determining the different attractions of the rod is this: Stand, holding the rod with one foot advanced; put a guinea under that foot, and an halfpenny under the other, and the rod will be drawn down; fhift the pieces of money, and the rod will be drawn towards the face, or backwards to the gold, which proves the gold to have the ftronger attraction. "The rods formerly ufed were fhoots of one year's growth that grew forked; but it is found, that two feparate fhoots tied together with packthread or other vegetable fubftance anfwer rather better than fuch as are naturally forked, as the fhoots of the latter are feldom of an equal fize. They are to be tied together by the greater ends, the fmall ones being held in the hands. Hazle rods cut in the winter, fuch as are used for fishing rods, and kept till they are dry, do beft; though, where these are not at hand, apple-tree fuckers, rods from peach-trees, currants, or the oak, though green, will anfwer tolerably well." Our author next proceeds to defcribe the manner of holding the rod; of which he gives a figure, as he fays it is difficult to be defcribed. The fmall ends being crooked, are to be held in the hands in a position flat or parallel to the horizon, and the upper part in an elevation not perpendicular to it, but at an angle of about 70 degrees. The rod (fays he) being pro F perly Mine. perly held by thofe with whom it will anfwer, when thefe additions it is not attracted." Such are the accounts of this extraordinary rod, to which it is probable that few will affent; and we believe the inftances of mines having been difcovered by it are but very rare. Another and very ancient mode of difcovering mines, lefs uncertain than the divining rod, but extremely difficult and precarious, is that called hodeing; that is, tracing them by loofe ftoncs, fragments, or fhodes, which may have been feparated and carried off to a confiderable diftance from the vein, and are found by chance in running waters, on the fuperficies of the ground, or a little under. "When the tinners (fays Mr Price) meet with a loofe fingle ftone of tin ore, either in a valley or in ploughing or hedging, though at Ico fathoms diftance from the vein it came from, those who are accustomed to this work will not fail to find it out. They confider, that a metallic flone muft originally have appertained to fome vein, from which it was fevered and caft at a diftance by fome violent means. The deluge, they fuppofe, moved moft of the loofe earthy coat of the globe, and in many places washed it off from the upper towards the lower grounds, with fuch a force, that moft of the backs or lodes of veins which protruded themselves above the faft were hurried downwards with the common mafs: whence the fkill in this part of their bufinefs lies much in directing their meafures according to the fituation of the furface." Afterwards, however, our author complains, that this art of fooding, as he calls it, is in a great measure loft. The following account of a method of finding filver mines by Alonzo Barba feems to be fimilar to that of hoding just now mentioned. "The veins of metal (fays he) are fometimes found by great ftones above Mine. "Another way (fays Mr Price) of difcovering lodes is by working drifts acrofs the country, as we call it, that is, from north to fouth, and vice verfa. I tried the experiment in an adventure under my management, where I drove all open at grafs about two feet in the fhelf, very much like a level to convey water upon a mill wheel: by fo doing I was fure of cutting all lodes in my way; and did accordingly difcover five courses, one of which has produced above 180 tons of copper ore, but the others were never wrought upon. This method of difcovering lodes is equally cheap and certain; for 100 fathoms in fhallow ground may be driven at 50s. expence." In that kind of ground called by our author feafille, and which he explains by the phrafe tenderflanding, he tells us, that "a very effectual, proving, and confequential way is, by driving an adit from the loweft ground, either north or fouth; whereby there is a certainty to cut all lodes at 20, 30, or 40 fathoms deep, if the level admits of it. In driving adits or levels across, north or fouth, to unwater mines already found, there are many fresh veins difcovered, which frequently prove better than those they were driving to." After the mine is found, the next thing to be confidered is, whether it may be dug to advantage. In order to determine this, we are duly to weigh the na ture of the place, and its fituation, as to wood, water, carriage, healthinefs, and the like; and compare the refult with the richness of the ore, the charge of digging, ftamping, washing, and fmelting. Particularly the form and fituation of the fpot fhould be well confidered. A mine muft either happen, 1. In a mountain; 2. In a hill; 3. In a valley; or, 4. In a flat. But mountains and hills are dug with much greater eafe and convenience, chiefly because the drains and burrows, that is, the adits or avenues, may be here readily cut, both to drain the water and to form gang-ways for bringing out the lead, &c. In all the four cafes, we are to look out for the veins which the rains or other accidental thing may have laid bare; and if fuch a vein be found, it may often be proper to open the mine at that place, especially if the vein prove tolerably large and rich: otherwife the moft commodious place for fituation is to be chosen for the purpose, viz. neither on a flat, nor on the tops of mountains, but on the fides. The best fituation for a mine, is a mountainous, woody, whole fome fpot; of a fafe cafy afcent, and bordering on a navigable river. The Mine. The places abounding with mines are generally healthy, as ftanding high, and every where expofed to the air; yet fome places where mines are found prove poifon ous, and can upon no account be dug, though ever fo rich: the way of examining a fufpected place of this kind, is to make experiments upon brutes, by expofing them to the effluvia or exlialations to find the effects. Devonshire and Cornwall, where there are a great many mines of copper and tin, is a very mountainous country, which gives an opportunity in many places to make adits or fubterraneous drains to fome valley at a distance, by which to carry off the water from the mine, which otherwife would drown them out from getting the ore. Thefe adits are fometimes carried a mile or two, and dug at a vaft expence, as from 2000l. to 4000l. especially where the ground is rocky; and yet they find this cheaper than to draw up the water out of the mine quite to the top, when the water runs in plenty and the mine is deep. Sometimes, indeed, they cannot find a level near enough to which an adit may be carried from the very bottom of the mine; yet they find it worth while to make an adit at half the height to which the water is to be raifed, thereby faving half the expence. The late Mr Coftar, confidering that fometimes from fmall freams, and fometimes from little fprings or collections of rain-water, one might have a good deal of water above ground, though not a fufficient quantity to turn an overhot-wheel, thought, that if a fufficient fall might be had, this collection of water might be made useful in railing the water in a mine to the adit, where it may be carrried off. But now the most general method of draining mines is by the fteam-engine. See STEAM-Eagine. MINE, in the military art, denotes a fubterraneous canal or paffage, dug under the wall or rampart of a fortification, intended to be blown up by gunpowder. The alley or paffage of a mine is commonly about four fect fquare; at the end of this is the chamber of the mine, which is a cavity of about five feet in width and in length, and about fix feet in height; and here the gunpowder is ftowed. The fauciffe of the mine is the train, for which there is always a little aperture left. Two ounces of powder have been found, by experiment, capable of railing two cubic feet of earth; confequently 200 ounces, that is, 12 pound 8 ounces, will raife 200 cubic feet, which is only 16 feet fhort of a cubic toife, because 200 ounces joined together have proportionably a greater force than 2 ounces, as being an united force. All the turnings a miner ufes to carry on his mines, and through which he conducts the fauciffe, fhould be well filled with earth and dung; and the mafonry in proportion to the earth to be blown up, as 3 to 2. The entrance of the chamber of the mine ought to be firmly fhut with thick planks, in the form of a St Andrew's crofs, fo that the inclofure be fecure, and the void fpaces fhut up with dung or tempered earth. If a gallery be made below or on the fide of the chamber, it muft abfolutely be filled up with the ftrongeft niafonry, half as long again as the height of the earth; for this gallery will not only burit, but likewife ob ftru&t the effect of the mine. The powder fhould al- Mine. ways be kept in facks, which are opened when the mine is charged, and fome of the powder ftrewed about: the greater the quantity of earth to be raised is, the greater is the effect of the mine, fuppofing it to have the due proportion of powder. Powder has the fame effect upon mafonry as upon earth, that is, it will proportionably raife either with the fame veiocity. The branches which are carried into the folidity of walls do not exceed three feet in depth, and two feet fix inches in width nearly this fort of mine is molt excellent to blow up the ftrongest walls. The weight of a cubic foot of powder fhould be 80 lb. 1 foot 1 inch cube will weigh 100 lb. and 1 foot 2 inches and, 150 lb. and 200 lb. of powder will be 1 foot 5 inches cube; however, there is a diverfity in this, according to the quantity of faltpetre in the gunpowder. If, when the mines are made, water be found at the bottom of the chamber, planks are laid there, on which the powder is placed either in facks or barrels of ico lb. each. The fauciffe must have a clear passage to the powder, and be laid in an auget or wooden trough, through all the branches. When the powder is placed in the chamber, the planks are laid to cover it, and others again acrofs thefe; then one is placed over the top of the chamber, which is fhaped for that purpose: between that and thofe which cover tha powder, props are placed, which fhore it up; fome inclining towards the outfide, others to the infide of the wall; all the void spaces being filled with earth, dung, brick, and rough tones. Afterwards planks are placed at the entrance of the chamber, with one across the top, whereon they buttress three ftrong props, whofe other ends are likewife propped again't another plank fituated on the fide of the earth in the branch; which props being well fixed between the planks with wedges, the branch fhould then be filled up to its entrance with the forementioned materials. The fauciffes which pafs through the fide branches must be exactly the fame length with that in the middle, to which they join: the part which reaches beyond the entrance of the mine is that which conveys the fire to the other three; the faucilles being of equal length, will fpring together. From a great number of experiments, it appears, 1. That the force of a mine is always towards the weakeft fide; fo that the difpolition of the chamber of a mine does not at all contribute to determine this effect. 2. That the quantity of powder mull be greater or lefs, in proportion to the greater or lefs weight of the bodies to be raifed, and to their greater or lefs cohefion; fo that you are to allow for each cubic fathom Of loofe earth, Firm earth and ftrong fand, Flat clayey earth, 9 or 10lb. 11 or 12 15 or 16 New masonry, not ftrongly bound, 15 or 25 25 or 30 3. That the aperture, or entonnoir of a mine, if rightly charged, is a cone, the diameter of whofe bafe is double the height taken from the centre of the mine. 4. That when the mine has been overcharged, its entonnoir is nearly cylindrical, the diameter of the upper F 2 extreme. Mineral, extreme not much exceeding that of the chamber. 5. That befides the fhock of the powder against the bodies it takes up, it likewife crushes all the earth that borders upon it, both underneath and fidewife. To charge a mine fo as to have the most advantageous effect, the weight of the matter to be carried must be known; that is, the folidity of a right cone, whofe base is double the height of the earth over the centre of the mine: thus, having found the folidity of the cone in cubic fathoms, multiply the number of fathoms by the number of pounds of powder neceffary for raifing the matter it contains; and if the cone contains matters of different weights, take a mean weight between them all, always having a regard to their degree of cohesion. As to the difpofition of mines, there is but one general rule, which is, that the fide towards which one would determine the effect be the weakeft; but this varies according to occafions and circumstances. The calculation of mines is generally built upon this hypothefis, That the entonnoir of a mine is the fruftum of an inverted cone, whofe altitude is equal to the radius of the excavation of the mine, and the diameter of the whole leffer base is equal to the line of least resistance; and though these fuppofitions are not quite exact, yet the calculations of mines deduced from them have proved fuccefaful in practice; for which reason this calculation fhould be followed till a better and more fimple be found out. M. de Valliere found that the entonnoir of la mine was a parabaloid, which is a folid generated by the rotation of a femiparabola about its axis; but as the difference between these two is very infignificant in practice, that of the fruftum of a cone may be used. MINERAL, in natural hiftory, is ufed in general for all foffile bodies, whether fimple or compound, dug out of a mine; from whence it takes its denomi nation. MINERAL Waters. All waters naturally impregna. ted with any heterogeneous matter which they have diffolved within the earth may be called mineral waters, in the mott general and extenfive meaning of that name; in which are therefore comprehended almost all thofe that flow within or upon the furface of the earth, for almost all thefe contain fome earth or felenites. But waters containing only earth or felenites are not generally called mineral, but hard or crude waters. Hard waters, which are fimply felenetic, when tried by the chemical proofs, fhow no marks of an acid or of an alkali, nor of any volatile, fulphureous, or metallic matters. Waters which contain a difengaged calcareous earth, change the colour of fyrup of violets to a green; and thofe that contain felenites, being mixed with a folution of mercury in nitrous acid, form a turbith mineral; and when a fixed alkali is added, they are rendered turbid, and a white fediment is precipitated. Thefe waters alfo do not diffolve foap well. From these circumftances we may know, that any water which produces thefe effects is a hard, earthy, or felenetic water. The waters impregnated with gas are alfo hard. Although the waters of the fea and faline fprings be not generally enumerated amongst mineral waters, they might nevertheless be juftly confidered as fuch: for befides earthy and felenetic matters, they alfo contain a large quantity of mineral falts. We shall therefore confider them as fuch in this article. Mineral waters, properly fo called, are thofe in Mineral. which gas, or fulphureous, faline, or metallic fubftan. →→→→ ces, are discovered by chemical trials. As many of these waters are employed fuccefsfully in medicine, they are also called medicinal waters. Mineral waters receive their peculiar principles by paffing through earths containing falts, or pyritous fubftances that are in a state of decompofition. Some of these waters are valuable from the quantity of useful falts which they contain, particularly of common falt, great quantities of which are obtained from these waters; and others are chiefly valued for their medi cinal qualities. The former kind of mineral waters is an object of manufacture, and from them is chiefly extracted that falt only which is most valuable in com merce. See SALT. Many of those waters have been accurately analysed by able chemists and physicians. But notwithftanding these attempts, we are far from having all the certainty and knowledge that might be defired on this important fubject; for this kind of analyfis is perhaps the most difficult of any in chemistry.-Almost all mineral waters contain several different substances, which being united with water may form with each other numberlefs compounds. Frequently fome of the prin ciples of mineral waters are in fo fmall quantity, that they can scarcely be perceived; although they may have fome influence on the virtues of the water, and alfo on the other principles contained in the water.The chemical operations used in the analysis of mineral waters, may fometimes occafion effential changes in the fubftances that are to be discovered. And also, these waters are capable of suffering very confiderable changes by motion, by reft, and by exposure to air. Probably alfo the variations of the atmosphere, fubterranean changes, fome fecret junction of a new fpring of mineral or of pure water, laftly the exhauftion of the minerals whence waters receive their peculiar principles, are caufes which may occafionally change the quality of mineral waters. We need not therefore wonder that the results of analyses of the fame mineral waters made by different chemifts, whose skill and accuracy are not queftioned, fhould be very different. The confequences of what we have faid on this fubje are, That the examination of mineral waters is a very difficult task; that it ought not to be attempted but by profound and experienced chemifts; that it requires frequent repetitions, and at different times; and laftly, that no fixed general rules can be given concerning thefe analyses. As this matter cannot be thoroughly explained without entering into details connected with all the parts of chemistry, we shall here mention only the principal refults, and the most effential rules, that have been indicated by the attempts hitherto made on this fubject. We may admit the divifion or arrangement of mineral waters into certain claffes, proposed by some of the best chemifts and naturalists. Some of thefe waters are called cold, because they are not naturally hotter than the atmosphere. Some of them are even colder, especially in fummer. Those are called hot mineral waters, which in all feafons are hotter than the air. Thefe are of various degrees of heat, and fome of them are almoft as hot |