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ticularly discoveries of coals and quarries.

Sometimes the crop and bearing of strata of coal run parallel to one of these ravines or gullies for a considerable length of ground, and sometimes they cross the glen or dingle in a right or a diagonal direction. When a stratum of coal crosses a glen in any angle whatever, there is a probability of discovering 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 some places in coal countries, to find the fuperficies of the strata washed clean by a river or rivulet in ftatu quo, that is, to find the feam or ftratum of coal in its proper regular position in the solid fuperficies of the strata, at full thick. ness and in perfect form betwixt roof and pavement, dipping towards the same point with the ordinary declivity of the ftrata in that place; but it is more common to discover in such 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 discovery.

I have all along in this history in culcated the neceffity of fome profici

ency in the natura! history of the various strata which compose the ftructure of the fuperficies of our globe, in order to qualify us for researches of this kind.

It is necessary for us in the prefent cafe to have some knowledge of the bearing and declivity of the strata, in the place where any indications of coal are found, before we can form any judgment of the discovery, and know how to make a proper use

of it.

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

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

I have shown already, that the outburst, or fuperficial vestigia 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 vestige will slide when the crop of the seam happens to be high up. I have also shown, that the extremity of the vestige of a coal feam at the surface is fometimes dissolved into a soft footy substance, hardly diftinguishable from a thin stratum of black clay or earth; however, the superficies of all coal feams are not so liable to be dissolved to that degree. The debris of some of the fplent and cannel coals frequently remain in hard and sharp masses of various fizes, even when mixt with the foil, and removed at some distance from the folid crop of the seam; and some of the cherry coals, or roch coals, as they are called in Scotland, de not diffolve upon the furface into an undiftinguishable mass like a friable clay; but, on the contrary, although the debris, or coal rubbish, at the surface should be broken very small, yet there will be found fome sharp angular grains and bits of coal, of the fize of pease, nuts, and plumbs. In places where seams of coal crop

out, fome appearance of the coal will be feen by an observing skilful eye in such glens as we have been speaking of. Sometimes masses of fplent or parrot, (i. e. cannel ccal), larger than a man's fist, will be found upon the fide or at the bottom of a ravine, which have flipt down by degrees from the crop of a seam of coal fituated above, and sometimes smaller bits like the thumb or lefs; but when the feam happens to be a cherry coal, the debris or vestige of the coal which has flipt down, is then a great deal smaller, very often like dust, and part of it in small diftinguishable grains, though perhaps no bigger than peafe.

From

From these inquiries it appears, that the veftigia and appearances of the outburst, or crops of different seams of coal, are of three forts: 1st, Pretty large masses of hard coal, not so apt to diffolve when exposed to the influence of the external air: 2d, Smaller masses and grains of cherry coal of a diced or cubic form, which is frequently mixt with a foot-like coal dust: and, 3d, Coal-duft, without any visible grains and masses, sometimes resembling foot, and sometimes hardly diftinguishable from a blackish 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 side or at the bottom of a glen or gully. Sometimes they are to be found appearing under the upper soil upon the face of the rock in some 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 strata are to be seen in the same glen, and to examine the points of the compass towards which the strata trend, and incline or dip; and when these points are afcertained, you will be enabled to know whether the strata run parallel to, or cross the glen, where the appearance is found. If the bearing of the strata is either parallel, or nearly parallel to the trending of the fides of the glen, you can eafily difcover the feam of the coal, by digging small pits at a proper diftance from one another, cutting thro' the veftigia of coal, and in a line up the flope; and if the last of these, that is, the upmost, should happen to have no vestige of coal, it is very probable that you have overshot 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 strata. If the bearing of the strata croffes the glen, either at right angles or in a diagonal direction, your digging then must be directed across the course and bearing of the strata; and perhaps in this case it may be more proper to dig a trench, in a line from the place where the vestige of coal is found, than to make pittings; the trench to run across the bearing of the strata; but of this those who are upon the spot must judge which, method of trial is best, as circumstances vary confiderably in different places.

But it frequently happens, that the superficies of the strata is not to be seen in several places, in many glens the face of the folids being often concealed under a deep or thick cover of gravel sand or clay.

It is very common in a coal country to find banks or beds of small gravel, and likewife beds of fand and clay, mixt with small masses of coal of various fizes, which indeed is an indication of your being in a coal country; but such bits of coal fo found are no indication of a feam of coal in this place; nevertheless, a seam, 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 these masses of coal were carried there when the rest of the sand or clay with which they are blended was lodged there by water; and, therefore, it is neceffary, when you find small masses 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, sand, 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 strata 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 sinking coal-pits, yet we more frequently fink through clay; and of all the species of clay, a strong, hard, and dry clay, mixt with less or more of fand, gravel, or stones, is the most common in coal-fields. When this species of clay is blended with boulders and bullets, with some gravel and fand, it is frequently very strong and dry, and almost as hard as a rock. In some places this species of compounded cover clay contains fpecimens of all the strata found in the neighbourhood; and when it is of this fort, which may be called a general composition, it is frequently a very curious and a very confufed mass of indigested matter. Grains, masses, and fragments of every species, quality, and colour of the strata to be found in that country, are promifcuously blended in this heterogeneous species of clay.

There are in some places vast beds and banks of these compounded clays, which cover and effectually conceal the fuperficies of the strata for a considerable extent; sometimes over the whole face of an extensive neighbourhood, excepting where it happens to be cut through by a strong current of water'; but it is sometimes so hard that the strongest currents are not able to wear it through. I have in many places seen this species of clay from a yard up to thirty or forty yards deep, and more, above the rock or fuperficies of the strata; and, as I hinted above, it frequently contains specimens of the coals, and of all other strata found in the neighbourhood. I have often seen such a quantity of larger and smaller masses of coal blended in this fort of clay in some particular places, as might deceive many, and make them imagine that it was the vestigia of the crop of a feam of coal. I know that many do imagine it, and I have no doubt that feveral will be induced, from the

quantity and variety of bits of coal found in different places in this clay, to make some trial in it; and for fuch as are not very well acquainted with this composition, perhaps it would be wrong to diffuade them altogether from digging a little in it, because it is in some instances pretty difficult, to distinguish between the vestige of the crop of a feam of coal, and a neft of bits and grains of coal blended in the compound clay; especially when we confider and know that a real outburst of the crop of a coal is frequently mixt with clay at the furface of the ground; and, therefore, when appearances are so doubtful that a gentleman cannot readily diftinguith with certainty whether the masses and grains of coal which he beholds are the vestigia 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 some little trial, is adventitious, and belonging to the compound clays, the symptoms will not alter much upon digging in it, there being fometimes a great depth of this clay above the superficies of the solid strata; 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 masses of coal in it; which coal is part of the compofition, and the whole mass of the clay, as well as the coal, is adventitious.

As several of these beds of compound clay contain specimens of all the strata of the neighbourhood, which is an evident fact, easily proved by comparing the specimens with the strata from which they were broken off; and as coal is a part of this composition, I give this as another fymptom or indication of coal, which may be called an infallible one. I cannot, it is true, by seeing this symptom of coal, pretend to say there is a feam of coal within so many yards, nor within

fo

To many hundred yards: I have nevertheless no difficulty to assert that there is coal in the neighbourhood where this compounded clay appears with masses and grains of coal in the composition.

I have been thus explicit in pointing out the difference between small masses of coal discovered 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 distinguish the one from the other.

After this explanation of the origin, appearance, and component parts of these beds of cover clay which so frequently conceal the fuperficies of the strata from our view, I hope that all gentlemen, even such as are not adepts in this science, will be able to distinguish between small masses or bits of coal found in these beds of clay, and such 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 distinguish between the vestige of the crop of a seam, which is generally continued, and increases from the first discovery until we find the crop of the seam 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 satisfied that they are digging in a bed of this fpecies of clay, it will be needless for them to proceed, there being no hopes of making any discovery in it.

There is one circumstance yet to be remarked. The masses and bits found in the compound clay are generally hard, clear, and perfect.; whereas the bits found in the vestigia of the crop of a feam of coal have frequently a decayed imperfect appearance, sometimes quite decomposed or diffolved into duft, resembling foot or black earth; and where there are small masses of coal, they are generally tender and friable, and blended with different quantities of diffolved coal dust, excepting in the case of the seam of coal containing a stratum of hard parrot or of hard splent, as these sometimes produce pretty large masses, which are found flidden down the flope, or scattered about the furface, at a confiderable diftance from the crop of the feam of coal. These larger masses frequently appear in confiderable degrees of perfection, without any other vestige of coal, at a distance from the seam, though other vestigia may be found nearer to it. Masses of cannel and hard splent coals bear tumbling about, and they bear the external influence and changes of the air without injury as well as some stones; but all the cherry coals, roch coals, and fome of the splents, decompofe at the furface, and fall either to dust or to small grains; and it frequently happens that fome parts of the fame stratum of coal diffolve to powder, and other parts of it fall down to small debris, or to grains and bits of various fizes; and these 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 superficies of the ftrata laid bare for their infpection; where they may see strata of coal, and its concomitant strata, both above and below, and likewise strata of ball-iron stone, which is now become an article of much value and confequence in Scotland.

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

The fuperficies of several of these seams of coal, and of their concomitant strata, are to be seen when the, tide is out, within flood mark, between Edinburgh and Muffelburgh, near Duddingston fire-engine; and there is a pretty good section of them to be seen in the high road (upon the left hand) from Edinburgh to Dalkeith, betwixt the parks of Drum and Edmondstone †. But the best sections of these coals, and of the strata which accompany them, are to be found and seen in the levels and crosscut mines in the coal-works of Gil

zontal strata of the coal metals, and of post freestone, to be seen in the bed, and upon the banks of the river Esk in several places, below the junction of the two branches of it, particularly near the corn-mills of Cowpits colliery, where some pretty good sections are to be seen in quarries upon both fides of the river, dipping towards the north and north-west, with an easy slope.

There are several sections 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 Roslin and Hawthornden, where abundance of high and romantic rocks appear upon both fides; but these rocks will not afford much instruction in this science, because they are chiefly.composed of thick strata of post free-stone, running parallel to the bed and course of the river, which causes a dull uniformity in the appearance of these rocks; I mean with respect to stratification; but as the rocky banks of a small river, they are abundantly magnificent and curious.

Between Roflin and Auchindinny bridge, there are several fine and lofty fections of the strata of coal metals upon both sides of the river, among which there are several thick beds of red and white post stone, with a variety of such other strata as commonly attend coal; and there are a confiderable number of coal feams both above and below these sections, many of which have been, and continue to be wrought. The sections of the strata