ticularly discoveries of coals and quarries.

Sometimes the crop and bearing of ftrata of coal run parallel to one of thefe ravines or gullies for a confiderable length of ground, and fometimes they cross the glen or dingle in a right or a diagonal direction. When a ftratum of coal croffes a glen in any angle whatever, there is a probability of difcovering the crop of the feam or fome indications of it, either in the bed of the rivulet or upon one fide of it.

It is not uncommon, in fome places in coal countries, to find the fuperficies of the strata wafhed clean by a river or rivulet in ftatu quo, that is, to find the seam or ftratum of coal in its proper regular pofition in the folid fuperficies of the ftrata, at full thick. nefs and in perfect form betwixt roof and pavement, dipping towards the fame point with the ordinary declivity of the strata in that place; but it is more common to discover in fuch places only fome appearances of coal, which frequently require knowledge and acuteness to difcern, with skill and judgment to make a proper use of the difcovery.

I have all along in this hiftory inculcated the neceffity of fome proficiency in the natura! history of the various ftrata which compofe the ftructure of the fuperficies of our globe, in order to qualify us for refearches of this kind.

It is neceffary for us in the prefent cafe to have fome knowledge of the bearing and declivity of the ftrata, in the place where any indications of coal are found, before we can form any judgment of the difcovery, and know how to make a proper ufe of it.

When a feam of coal runs parallel to a glen or gully, and crops out any where within the banks upon one fide or the other, there is a great chance of discovering fome indications of the

coal, perhaps in feveral places as you advance up or down the glen.

I have shown already, that the outburst, or fuperficial veftigia of a stratum of coal, upon a flope, is always found to flide downwards, and that the longer and more precipitate the flope is, the farther down the veftige will flide when the crop of the feam happens to be high up. I have also shown, that the extremity of the veftige of a coal feam at the furface is fometimes diffolved into a foft footy substance, hardly diftinguishable from a thin ftratum of black clay or earth; however, the fuperficies of all coal feams are not fo liable to be diffolved to that degree. The debris of fome of the fplent and cannel coals frequently remain in hard and sharp maffes of various fizes, even when mixt with the foil, and removed at fome distance from the folid crop of the feam; and fome of the cherry coals, or roch coals, as they are called in Scotland, do not diffolve upon the furface into an undiftinguishable mafs like a friable clay; but, on the contrary, although the debris, or coal rubbish, at the furface fhould be broken very fmall, yet there will be found fome of the fize of peafe, nuts, and plumbs. fharp angular grains and bits of coal, In places where feams of coal crop out, fome appearance of the coal will in fuch glens as we have been fpeakbe feen by an obferving fkilful eye ing of. Sometimes maffes of fplent or parrot, (i. e. cannel ccal), larger than a man's fift, will be found upon the fide or at the bottom of a ravine, which have flipt down by degrees from the crop of a feam of coal fituated above, and fometimes fmaller bits like the thumb or lefs; but when the feam happens to be a cherry coal, the debris or veftige of the coal which has flipt down, is then a great deal smaller, very often like duft, and part of it in fmall diftinguishable grains, though perhaps no bigger than peafe.

From

:

From thefe inquiries it appears, that the veftigia and appearances of the outburst, or crops of different feams of coal, are of three forts: 1ft, Pretty large maffes of hard coal, not fo apt to diffolve when expofed to the influence of the external air: 2d, Smaller maffes and grains of cherry coal of a diced or cubic form, which is frequently mixt with a foot-like coal duft and, 3d, Coal-duft, without any vifible grains and maffes, fometimes resembling foot, and fometimes hardly diftinguishable from a blackith or dark brown friable earth. One or other of these veftigia or appearances of coal are frequently to be found mixt with the upper foil upon the fide or at the bottom of a glen or gully. Sometimes they are to be found appearing under the upper foil upon the face of the rock in fome break or fcar.

When any of these appearances are discovered within the banks of a ravine or glen, the first thing to be done is to go to a place where the fuperficies of the ftrata are to be seen in the fame glen, and to examine the points of the compafs towards which the ftrata trend, and incline or dip; and when thefe points are afcertained, you will be enabled to know whether the ftrata run parallel to, or cross the glen, where the appearance is found. If the bearing of the ftrata is either parallel, or nearly parallel to the trending of the fides of the glen, you can eafily discover the feam of the coal, by digging fmall pits at a proper diftance from one another, cutting thro' the veftigia of coal, and in a line up the flope; and if the laft of thefe, that is, the upmost, fhould happen to have no veftige of coal, it is very probable that you have overfhot the feam, and in that cafe you must go back to the next pitting in which the appearance of coal was found, and dig a cross cut in a line upwards, and you cannot fail to cut the furface or crop of the feam of coal, if you dig

to the face of the rock or folid ftrata. If the bearing of the ftrata croffes the glen, either at right angles or in a diagonal direction, your digging then must be directed across the courfe and bearing of the ftrata; and perhaps in this case it may be more proper to dig a trench, in a line from the place where the veftige of coal is found, than to make pittings; the trench to run across the bearing of the ftrata; but of this thofe who are upon the fpot muft judge which method of trial is beft, as circumftances vary confiderably in different places.

But it frequently happens, that the fuperficies of the ftrata is not to be feen in feveral places, in many glens the face of the folids being often concealed under a deep or thick cover of gravel fand or clay.

It is very common in a coal coun-' try to find banks or beds of fmall gravel, and likewife beds of fand and clay, mixt with fmall maffes of coal of various fizes, which indeed is an indication of your being in a coaf country; but fuch bits of coal fo found are no indication of a feam of coal in this place; nevertheless, a feam, or feams, of coal may be there, but the bits of coal lodged in the banks of fand or clay are not the veftigia of them, as thefe maffes of coal' were carried there when the rest of the fand or clay with which they are blended was lodged there by water; and, therefore, it is neceffary, when you find fmall maffes and grains of coal, to be able to judge whether they are mixt with the natural foil, or in adventitious beds or banks of

gravel, fand, or clay. If amongst adventitious matter, you need not dig, unless you have fome other more certain indications of a feam of coal being near.

Of all the beds and banks of adventitious matter which are found above, and conceal the fuperficies of the folid ftrata from our view, clay, is the most common in coal countries;

though

though it frequently happens that we have to dig through fand or gravel in finking coal-pits, yet we more frequently fink through clay; and of all the fpecies of clay, a ftrong, hard, and dry clay, mixt with lefs or more of fand, gravel, or stones, is the most common in coal-fields. When this fpecies of clay is blended with boulders and bullets, with fome gravel and fand, it is frequently very ftrong and dry, and almost as hard as a rock. In fome places this fpecies of compounded cover clay contains fpecimens of all the ftrata found in the neighbourhood; and when it is of this fort, which may be called a general compofition, it is frequently a very curious and a very confufed mafs of indigefted matter. Grains, maffes, and fragments of every species, quality, and colour of the ftrata to be found in that country, are promifcuously blended in this heterogeneous fpecies of clay.

There are in fome places vaft beds and banks of thefe compounded clays, which cover and effectually conceal the fuperficies of the ftrata for a confiderable extent; fometimes over the whole face of an extenfive neighbourhood, excepting where it happens to be cut through by a strong current of water; but it is fometimes so hard that the strongest currents are not able to wear it through. I have in many places feen this fpecies of clay from à yard up to thirty or forty yards deep, and more, above the rock or fuperficies of the ftrata; and, as I hinted above, it frequently contains fpecimens of the coals, and of all other ftrata found in the neighbour hood. I have often feen fuch a quantity of larger and fmaller maffes of coal blended in this fort of clay in fome particular places, as might deceive many, and make them imagine that it was the veftigia of the crop a feam of coal. I know that many do imagine it, and I have no doubt that feveral will be induced, from the

of

quantity and variety of bits of coal found in different places in this clay, to make fome trial in it; and for fuch as are not very well acquainted with this compofition, perhaps it would be wrong to diffuade them altogether from digging a little in it, because it is in fome inftances pretty difficult, to distinguish between the veftige of the crop of a feam of coal, and a neft of bits and grains of coal blended in the compound clay; efpecially when we confider and know that a real outburft of the crop of a coal is frequently mixt with clay at the furface of the ground; and, therefore, when. appearances are fo doubtful that a gentleman cannot readily diftinguish with certainty whether the maffes and grains of coal which he beholds are the veftigia of a feam or adventitious, it may be proper for him to dig a little. If the appearance of coal, upon which he is going to make fome little trial, is adventitious, and belonging to the compound clays, the fymptoms will not alter much upon digging in it, there being fometimes a great depth of this clay above the fuperficies of the folid itrata; and, therefore, he will not find any material change in digging. He will find no appearance of any difcovery; there is nothing but the fame compound clay continuing with adventitious grains and maffes of coal in it ; which coal is part of the compofition, and the whole mafs of the clay, as well as the coal, is adventitious.

;

As feveral of thefe beds. of compound clay contain fpecimens of all the ftrata of the neighbourhood, which is an evident fact, eafily proved by comparing the fpecimens with the ftrata from which they were broken off; and as coal is a part of this com pofition, I give this as another fymptom or indication of coal, which may be called an infallible one. I cannot, it is true, by feeing this fymptom of coal, pretend to fay there is a feam of coal within fo many yards, nor within

fo

fo many hundred yards: I have nevertheless no difficulty to affert that there is coal in the neighbourhood where this compounded clay appears with maffes and grains of coal in the compofition.

I have been thus explicit in pointing out the difference between fmall maffes of coal difcovered in the compound clay, and the real veftigia of the crop of a feam of coal, for the information of fuch as cannot yet perfectly diftinguish the one from the other.

After this explanation of the origin, appearance, and component parts of thefe beds of cover clay which fo frequently conceal the fuperficies of the ftrata from our view, I hope that all gentlemen, even fuch as are not adepts in this fcience, will be able to diftinguish between fmall maffes or bits of coal found in thefe beds of clay, and fuch as belong to the real outburst or crop of a feam of coal; and in cafes where they are not certain at first, and refolve to dig, they will foon be able to diftinguish between the veftige of the crop of a feam, which is generally continued, and increases from the first discovery until we find the crop of the feam betwixt roof and pavement; whereas the bits found blended in the compound clay are generally detached from one another, are imbedded in a vast mass of clay, without any continued ftratum or veftigia which might lead to a feam of coal; and, therefore, when gentlemen are fatisfied that they are digging in a bed of this fpecies of clay, it will be needlefs for them to proceed, there being no hopes of making any discovery in it.

There is one circumftance yet to be remarked. The maffes and bits found in the compound clay are generally hard, clear, and perfect; whereas the bits found in the veftigia of the crop of a feam of coal have frequently a decayed imperfect appearance, fometimes quite decompofed or diffolved into dust, refembling foot or black earth; and where there are fmall maffes of coal, they are generally tender and friable, and blended with different quantities of diffolved coal duft, excepting in the cafe of the feam of coal containing a ftratum of hard parrot or of hard fplent, as thefe fometimes produce pretty large maffes, which are found flidden down the flope, or fcattered about the furface, at a confiderable diftance from the crop of the feam of coal. Thefe larger maffes frequently appear in confiderable degrees of perfection, without any other veftige of coal, at a diftance from the feam, though other veftigia may be found nearer to it. Maffes of cannel and hard fplent coals bear tumbling about, and they bear the external influence and changes of the air without injury as well as fome ftones; but all the cherry coals, roch coals, and fome of the fplents, decompofe at the furface, and fall either to duft or to small grains; and it frequently happens that fome parts of the fame ftratum of coal diffolve to powder, and other parts of it fall down to fmall debris, or to grains and bits of various fizes; and thefe are found blended together either upon the furface of the ground, or under the cover clay, or other matter.

VOL. XI. No. 64.

Kk

Enumeration

258

I

SHALL here point out a few of the many places in the Lothians, where the lovers of mineral knowledge may behold the fuperficies of the ftrata laid bare for their infpection; where they may fee ftrata of coal, and its concomitant ftrata, both above and below, and likewife ftrata of ball-iron ftone, which is now become an article of much value and confequence in Scotland.

The vertical or edge feams of Gilmerton and Loanhead are the nearest coals to Edinburgh, of any that have been yet difcovered and wrought.

The fuperficies of feveral of thefe feams of coal, and of their concomitant ftrata, are to be feen when the, tide is out, within flood mark, between Edinburgh and Muffelburgh, near Duddington fire-engine; and there is a pretty good fection of them to be feen in the high road (upon the left hand) from Edinburgh to Dalkeith, betwixt the parks of Drum and Edmondstone t. But the beft fections of thefe coals, and of the ftrata which accompany them, are to be found and feen in the levels and crofscut mines in the coal-works of Gil

merion.

The rivers North and South Efk, in Mid-Lothian, cut through a remarkably rich coal-field. These two rivers join in one before they reach Muffelburgh, where the united Ek falls into the tide. Though the two Efks are but fmall rivers, yet they have in many places fcooped out or worn very deep channels; and there are many fine fections of the ftrata of coal metals to be feen upon their banks in the deep ravines.

There are good and regular hori

zontal ftrata of the coal metals, and of poft freeftone, to be feen in the bed, and upon the banks of the river Elk in feveral places, below the junction of the two branches of it, particularly near the corn-mills of Cowpits colliery, where fome pretty good fections are to be feen in quarries upon both fides of the river, dipping towards the north and north-west, with an easy flope.

There are feveral fections of the flat or horizontal coal metals, a little way above the ford of the North Esk upon the Newbattle road from Edinburgh, and likewife below the ford near the iron mills.

The bed or channel of this river is remarkably deep about Rollin and Hawthornden, where abundance of high and romantic rocks appear upon both fides; but thefe rocks will not afford much inftruction in this fcience, because they are chiefly compofed of thick ftrata of poft free-ftone, running parallel to the bed and course of the river, which caufes a dull uniformity in the appearance of these rocks; I mean with refpect to ftratification; but as the rocky banks of a fmall river, they are abundantly magnificent and curious.

Between Rollin and Auchindinny bridge, there are feveral fine and lofty fections of the ftrata of coal metals upon both fides of the river, among which there are feveral thick beds of red and white poft ftone, with a variety of fuch other ftrata as commonly attend coal; and there are a confiderable number of coal feams both above and below thefe fections, many of which have been, and continue to be wrought. The fections of the ftrata

is levelled and planted,