attained a depth of 6,5727 feet, or 2,003'34 metres. The surface level of this boring being 4987 feet higher than that of Schladebach, it only penetrated 338 feet nearer the centre of the earth than the Schladebach boring. The Paruschowitz borehole proved the existence of eighty-three coal-seams, many of them being of considerable thickness, and giving a total thickness of 89.5 m., or 293 6 feet. Begun with a diameter of 12 inches, and lined with a tube 12 inch thick, the boring was put down to a depth of 230 feet, from which point to 351 feet the diameter was reduced to 10 inches. At this depth the blue marls encountered became so compact as to necessitate the use of the diamond drill for the further boring. Under the action of the water injected into the hole, the marl swelled and subjected the lining tubes to such compression that it was found necessary to gradually reduce their diameter. Shifting sand, met with at the depth of about 656 feet, also caused great difficulty. The greatest difficulty of all, however, was the great weight of the boring-rods as the depth increased. Although a reduction in the weight of these was obtained by substituting steel for iron, yet at the depth of 6,560 feet the total weight of the tools was 13.7 tons. With such a weight and so great a length, ruptures of the rods were frequent, and an accident of this nature finally stopped the work. When the diameter was 233 inches, and that of the cores brought up 135 inches, about 4,500 feet of rods fell to the bottom, and became jammed in an unlined portion under the tubing, so that it was impossible to withdraw them. Consequently the borehole was abandoned. During the 399 working days a daily advance of a little over 16 feet was made. The total cost of the boring was £3,761, or 34s. 4d. per yard. Temperature observations made showed 12.1° Cent., or 54° Fahr. at the surface, and at a depth of 6,572.7 feet the 'temperature reached 693° Cent. or 157° Fahr. This gives an average increase of 1° Cent. for 34°14 m., or 1° Fahr. for 63 feet, differing from that observed at Schladebach, where the mean increase was 1° Cent. for a depth of 35'45 m., or 1° Fahr. for every 64 feet 7 inches. During thirteen years the Prussian Government have made 400 boreholes for exploring purposes, of an aggregate depth of 80 miles, and at a cost of £650,000. A bore-hole at Sperenberg, Berlin, was made by means of rigid rods to a depth of 4,170 feet, and took 4 years to accomplish. A boring for salt near Lubtheon, in Mecklenburg, was carried out by a diamond drill to nearly 4,000 feet, and was completed within 6 months. The boring was not only wonderfully successful in the speed with which it was accomplished, but was further distinguished by the hole yielding 100 per cent. of cores, one specimen of rock-salt being over 20 feet long. No virgin property of a size to require any borings on it should have less than three, and it may be wise to put down more; but in a neighbourhood free from faults and dykes, and proved by winnings all round, none will be necessary. It is natural to let the first be nearest the rise. It must be remembered that the depths as proved by boring through inclined strata do not give the true thicknesses of such, as the bore-hole is perpendicular and the line of stratification does not often form a right angle to it. The true thickness of a stratum is found by multiplying the thickness as proved in the boring by the cosine of angle of dip. Thus, if a stratum was proved to be 1 fathom thick in the boring where the dip was at an angle of 30°, the true thickness would be ·866025 of a fathom or 5*19615 feet. Tables of incline measure may be obtained showing the comparative lengths of the hypothenuse, horizontal, and vertical legs of a right-angled triangle for every degree of the quadrant. Supposing three bore-holes to be put down on a property at equal distances apart, say 500 yards. No. 1 being nearest the rise and proving the coal at a depth of 15 fathoms, No. 2 fully to the dip of No. 1, as well as can be ascer tained, proving the same seam at a depth of 30 fathoms, and No. 3 still fully to the dip of No. 2 as nearly as may be judged, proving the same seam at a depth of 50 fathoms, all the bore-holes being at the same surface level. It would appear Fig. 17.-PLAN SHOWING POSITION OF BORE-HOLES. SCALE 6 CHAINS TO 1 INCH. that the dip of the strata from No. 1 to No. 2 bore-hole was 500 ÷ 60 yards = 16.6, that is, 1 in 16.6, and from No. 2 to No. 3, 500 ÷ 100 30 yards 60 = = 500 40 500 30 = 125, that is, I in 125, supposing there were no faults or dis locations in the strata to upset the calculation. Suppose now 4 bore-holes are put down on a property, and there are no other means of forming any idea of the dip. No. I proves the coal at a depth of 85 fathoms, No. 2 is due South of No. 1, by the magnetic needle, and proves the coal at 80 fathoms, being 500 yards from No. 1. No. 3 lies S. 50 E. of No. 1, and is 300 yards distant, proving the coal at a depth of 110 fathoms. No. 4 is S. 40 W. of No. 1, 250 yards distant from No. 1, and proves the coal at 64 fathoms, all the bore-holes being at the same surface level. The direction of full dip and its extent may be determined as follow. = By plotting as shown in Fig. 17, or by trigonometry, it will be found that the distance between No. 2 and No. 3 would be 383 62 yards. The difference in level between the seam at No. 2 and No. 3 bore-holes is 220 yards 160 = 60 yards and 383.62 639, that is the seam dips from No. 2 towards 60 No. 3 at the rate of 1 in 6:39. Now, to find the level course of the seam, follow along the course from No. 2 towards No. 3 until a point is reached 5 fathoms or 10 yards below the seam at No. 2 bore-hole, because the difference in the depth between No. I and No. 2 is 85 80 5 fathoms. To gain 10 yards of fall along a course dipping 1 in 6.39 follow it for a distance of 6.39 x 10 = 63'9 yards. Therefore a line drawn from No. 1 bore-hole to a point in the line connecting No. 2 and No. 3, and 63'9 yards distant from No. 2, gives the level course of the seam, and by means of plotting or from the computed value of the angles, it may be seen that the bearing from Nos. 2 to 3 bore-holes is N. 36° 48′ 9′′ E., and that of the level course of the seam S. 4° 52′ 29′′ E. from No. 1. The full dip would be at right angles to this or N. 85° 7′ 31′′ E. To get the amount of dip, draw a line connecting No. 3 bore-hole with the level course of the seam and at right angles to it. Such a line would measure 212'6 yards, and since the difference of level in the seam between the two ends of it is 110 fathoms 85 = 25 212.6 fathoms, or 50 yards, we have = 425, so that the full dip would be 1 in 50 4 25 in a direction N. 85° 7′ 31′′ E. In the same way it can be shown that a line drawn from No. 4 bore-hole to join the line representing the level course of the seam and at right angles to it would measure 176'4, and taking the dip at 1 in 4 25 as proved on the other side 176'4 of the level course = 415 yards or 20'75 fathoms, and 85 20'75 = 4°25 46.25 fathoms as the depth of No. 4 bore-hole to prove the seam, which is the depth given, a reasonable conclusion from which would be that the coal on the property was fairly free from faults. It is only right to say that these calculations are often upset by faults running between the position of the bore-holes, and when these are suspected to be on the property, more bore-holes should be put down before the sinking is decided on. In coalfields having carboniferous rocks exposed on the surface the outline of the basin may be traced by following the course of outcrop of the upper edge of millstone grit or other strata underlying the carboniferous, if conformable to them. Any estate being within the coal measure or productive area as shown on a geological map would usually be expected to comprise coal seams. situated to the rise of the lowest seam's outcrop, no coal would be available, although the rocks might belong to the lower members of the carboniferous period. If Where a coalfield is known to exist over a certain extent of country by its coal-bearing portion of the carboniferous rocks outcropping in some places and disappearing in others under Permian or newer rocks, which lie unconformably on them, there is much room for speculation as to the extent of the coalfield. Under such circumstances the search for coal of course becomes far more intricate. As an instance of the difficulties of such a search may be cited that of the South Staffordshire Coalfield under the "red rocks."* A fault which exists in the neighbourhood of West Bromwich appeared to cut off the coal measures * See Colliery Guardian, May 14th, 1875. which are exposed to the westward. To the east of this fault the coal measures are covered by "red rocks." About 1839 the Earl of Dartmouth sank the Heath Pits of a mile or thereabouts to the east of the boundary fault, and these pits passed through Lower Permian rocks overlaying the coal measures and proved thin seams of coal, thus showing that a further productive area existed of unknown length, but of a mile in width. As the Heath Pits did not find the Staffordshire thick coal, a "heading" was driven eastward, and a boring upwards from the end of the heading proved "red rock," while another downwards from the same point struck a hard rock, afterwards believed to be Silurian. After these failures to find the thick coal, one of the thin seams was followed to the west, towards the old or previously known portion of the coalfield, and this led into the thick coal. Sir Roderick Murchison was of opinion that the shaft had been sunk upon a line of dislocation, the continuation of the upcast of Silurian rocks of Walsall and Thame Bridge. Professor Jukes thought there was a sudden rise of Silurian rocks through the coal measures, forming a bank, and that this bank had been favourable to the formation of sandstone and the accumulation of clay, but unfavourable to the formation of coal. Silurian shale having been found in a pit at Langley Mill, Oldbury, Professor Jukes assumed the bank to be continuous for that distance -about three miles. While opinions differed as to what lay to the east of this bank, none were favourable to the existence of workable coal seams. Sinkings as indicated below in the newly-found tract of productive coal measures were stated to have proved various thicknesses of red rock (Permian) resting on various thicknesses of coal measures believed to have been denuded. Lewisham Pits Lyng Colliery Heath Pits Bullock's Farm Pits Unitt's Boring at the Permian over coal measures. 315 feet 550 806 Coal measures over thick coal. 520 feet. 350 "Ruck of Stones"},664 It was thought that these sinkings indicated a thickening of Permian beds to the eastward, while the coal measures below would unconformably be still further denuded. Professor Jukes considered it probable that a little further to the east of the Heath Pits, the coal measures would be entirely wanting, and the Permian rest directly on the shale of the Silurian formation. The boring at the "Ruck of Stones" lies more than a mile east of Bullock's Farm Pits; and the fact that the strata between them have a dip eastward of about 10 degrees, shows that the 700 feet of Permian at Bullock's Farm are wholly below the 664 feet proved at the "Ruck of Stones." From this Professor Jukes estimated that in the neighbourhood of West Bromwich there must be at least a total thickness of 1,500 feet of Permian rocks. On the assumption that the coal measures had not been subject to denudation and that the rocks to the eastward of the Silurian bank retained a normal thickness, it was argued that in any sinking for thick coal 1,500 feet of Permian and 1,000 feet of upper coal measures might be expected before reaching it. For many years these opinions of geological authorities had the effect of preventing trials on the doubtful ground, but at last the Sandwell Park Colliery Company, under the direction of Mr. Henry Johnson, made the venture, and as a reward for their enterprise struck the thick coal at 418 yards from the surface about the beginning of 1875 were The red rocks at Bullock's Farm and other West Bromwich sinkings were proved by the Sandwell Park sinkings to be coal measures instead of Permian as previously supposed. The Sandwell Pit is a mile to the eastward of Bullock's Farm. As fixing the position in the pit where the coal measures struck, fossil plants found at a depth of 110 yards in red measures were stated by authorities on the subject, to be Permian. At a depth of 200 yards a thin seam of coal 7 inches thick was proved. Above the coal was a black shale containing fossil plants, some of which were identical with those found at 110 yards, whilst beneath the coal was a bed of fire-clay containing Stigmaria. At 230 yards a second coal seam 6 inches thick was struck, and a third of the same thickness at a depth of 244 yards, while at 418 yards the thick coal, the object of this patient and enterprising search, was attained. The shaft therefore entered the coal measures at a depth of 110 yards or less, showing that there is a greater thickness of coal measures over the thick coal at Sandwell Park Colliery than was proved by the pits previously sunk through the Permian strata. As another instance of a successful search for coal we may mention that near Dover, in Kent. This discovery is full of interest to the geologist, and as it is within a workable depth it may create a very important industry in the South of England. Previously, no true coal had been found in England to the south of a line joining Bath and Stamford and continued to Great Yarmouth, though lignites were known to exist in the Wealden strata of Kent, Surrey, and Sussex. An examination of the formations (which are much newer than the carboniferous) prevailing over most of the area indicated would of itself not appear hopeful, yet geologists have reasoned for many years that there was a possibility of finding coal under these newer formations and within a reasonable distance of the surface. About the year 1855 Mr. Godwin-Austen started this theory, but Sir R. Murchison disputed it. In 1871 the Royal Coal Commission published its Report, including a very elaborate communication from Professor Joseph Prestwich, who had accepted the theory suggested by Mr. Godwin-Austen. The main feature which gave rise to the theory, is the fact that a great axis of elevation extends from the South of Ireland to Westphalia, a distance of 850 miles. Its existence can be traced at one extremity from Ireland to Frome in Somersetshire. Along the strike the lateral pressure elevated the fractured ends of the strata into ranges of hills, of which there now remain two remnants, viz., the Mendips, in Somersetshire, and the Ardennes, in Belgium. The Ardennes have many features in common with the Mendips. On the northern flanks of both ranges the paleozoic strata are highly inclined as if tilted up from the same disturbing cause, and both are overlaid by newer strata reposing horizontally on them. From Westphalia to the North of France there is a series of coalfields, the more important being those of the Ruhr, Aix-la-Chapelle, Liége and that of Charleroi, Mons, and Valenciennes, whose longer axes succeed one another along the same line of strike. In all these the coal measures are highly inclined on the south against the Mountain Limestone, while on the north they disappear under newer formations. Westward of Valenciennes no palæozoic strata are exposed on the surface, but the coal measures have been proved to pass beneath the chalk and tertiary strata to Enquin within 30 miles of Calais, whilst further west the older rocks subtend the chalk. A boring at Calais, however, proved carboniferous strata at a depth of 1,032 feet from the surface after passing through the chalk. Passing to a point near the other extremity of the same axis of elevation, a striking resemblance in the geological features is seen. From Milford Haven to Tenby are found old red sandstone and mountain limestone in a contorted |