1088 THE COLLIERY GUARDIAN. June 9, 1916. ous instrument. . . . the best description of lamp to bo employed is that on the principle of the improved Claimy and the Mueseler lamps, the latter with a continuous gauze cylinder.” During this period Clanny produced two more lam pts (his fifth and sixth), and Mueseler invented his lamp with the chimney. Clanny’s fifth lamp consisted of an internal gauze cylinder completely surrounded by an impervious metallic shield having glass and lenses in its side and only open at the highest part of the gauze cylinder for about l-J-in. from the top. There was a 1 in. air space between the cylinder and gauze, and air could only enter the lamp after passing over the top of the shield. The lamp was subse- quently modified by surrounding the portion opposite the flame with a “ thick globular ” shield of glass. The sixth lamp was constructed on the plan of the well-known Clanny, namely, with a glass cylinder surrounding the flame and a gauze cylinder doubled at the top fitted closely on to the glass. The Mueseler lamp tested by the Belgian committee introduced the chimney inside the gauze, and was similar in construction to the present unbonneted Mueseler. Period 1844 to 1866.—During this period three select committees were appointed in England to enquire into accidents, in mines. The reports of the first two com- mittees criticised the Davy lamp on the score of giving defective light and want of security in a strong explosive current. The third committee pointed out that opinions as to its security varied, but the majority were in its favour. In this period a considerable number of lamps of both types were introduced, including the “ Jack ” lamp, a shielded Davy in which the gauze was protected by a glass cylinder that extended from a short distance above the bottom of the gauze to the bottom of short gauze cap or smoke cap. The “ Tin-can ” Davy (1866) consisted of a Davy lamp closed in a tin casing with a glass window. To give a better light the “ Reflecting ” lamp was introduced, polished gauze being used and a polished cone being placed below the flame to reflect the light. Two gauze cylinders were used, the inner one “ being placed at such a distance from the outer that the fire- damp enclosed between the cylinders (if the flame passes the first) explodes and may extinguish itself.” Period 1867 to 1879.—During this period investigations were conducted by the North of England Institute of Mining and Mechanical Engineers; the ' Belgian Government; the Socidte de I’lndustrie Minerale in France; and Messrs. Smethurst and Ashworth. 'Several new lamps were introduced, but the only new type of lamp was the Gray, the, tendency being to attain a high degree of safety by increasing the complexity of con- struction. The results of the various investigations _ showed the insecurity of the Davy in currents exceeding 7 to 8ft. per second; and in the report of the French experiments the use of the shield (ecrari) was advocated. In Belgium the use of the Mueseler type of lamp was made obligatory in fiery mines. The experiments of- Messrs. Smethurst and Ashworth confirmed Davy’s results on restricting the diameter of the gauze cylinder. Period 1880 to 1887.—In addition to the following commissions : the French Firedamp Commission of 1878-1882, the Prussian Firedamp Commission of 1880-1887, the Saxon Firedamp Commission of 1880, and the British Royal Commission of 1879-1886, experi- ments were carried out by the Midland Institute of Mining, Civil, and Mechanical Engineers in 1884; by Mr. A. R. Sawyer in 1884-1885; and by the Mining Institute of Scotland in 1886. The reports of these com- missions contributed materially to the growth of knowledge on the subject. The importance of the shield or bonnet in increasing the safety was frequently insisted on, but its use was in some cases objected to, as it con- cealed the gauze from inspection. Among the lamps designed and tested was the Marsaut lamp, which was originally a bonneted Boty or Clanny, with a chimney, derived from the Mueseler by suppression of the gauze diaphragm; but subsequently the gauze diaphragm and Mueseler chimney-were replaced by an interior gauze. The large surface of this additional gauze offered means for the better cooling and escape of the gases. The gauzes were protected by a bonnet, with holes at the bottom for the admission of air, which was taken in over the glass and had to pass through both gauzes and holes at the top for the escape of the products of combustion. Period 1888 to 1913.—The most striking features of this period are the large number of official stations erected for testing safety-lamps and the improvement in apparatus used : in Great Britain (at Eskmeals), France, Belgium, Westphalia, Silesia, and Saxony, whilst the Austrian station at Mahrisch-Ostrau used by the com- mission 1881 to 1891 appears to have been maintained. Experiments were also carried out at Karwin. Considerable improvements have been made in the construction of lamps so as to secure strength in the various parts and to facilitate the operations of cleaning and assembling. Much attention has been given to the question of locking arrangements, and magnetic locks have come largely into use. Arrangements for lighting lamps by electric means after they have been assembled have been largely adopted, and in Great Britain, France, and Belgium the efficacy of the bonnet has been fully recognised. In France, Belgium, and Germany the use of internal relighters is very generally approved, but not so in Great Britain. The question of iliumin ants has also received much attention, and even acetylene lamps have been introduced. Among the more important lamps of this period may be mentioned the Howat “Deflector” lamp, the Ashworth-Hepplewhite-Gray, the Thorneburry, the Fumat, the Body-Firket, the Wolf, and the Hailwood “Combustion-tube” lamp. As the result of recent experiments, there has been a tendency to restrict the use of lamps by legislation to “ permitted ” lamps. This has been done in Great Britain, France, .and Belgium. Some Effects of Earth Movement on the Coal Measures of the Sheffield District, etc.—Part II.* By Prof, W. G. FEARNSIDES, M.A. (Continued f rom page 1040J Geometry of the Surface of the Barnsley Seam of Coal. Leaving for the moment the further discussion of the form and lateral extent of the pre-permian surface, the writer will pass to the (application of similar methods for obtaining, contours of the. surface of a seam of coal, the Barnsley bed (and its equivalent the Top Hard coal. of Derbyshire) being chosen first. The surface to which erosion pared down the coal measures is the surface which, by later tilting and gentle folding, has attained the geometry previously discussed by the writer. The geometry of one bed. in the measures, which is bent into folds and faulted, is the subject for the present investigation. After correction for the height above sea-level at which sinking or boring operations were begun, the list. of working pits or boreholes from which useful information as to depths is available is as follows :— Pit. Height Heigh t.UPy ClLvv • Ft. Ft. Ft. § Silver Hill ... + 400 — ... — i§Tibshelf + 400... — ... - !§ Alfreton + 375... — ... — §Blackwell + 350... ... — §Holmwood ... + 300... — ... — §Grassmoor ... + 220... — ... — New Stubbin + 160... — ... — Barugh (Red- brook) + 160 .. — — §Swanwick + 150... — ... — Low Laithes + 140... — ... — §S wan wick (Deep) + 100 .. — ... -- Handsworth.. + 124... —- ... — Lofthouse-I- 90... — ... — South Nor- manton + 90 .. — ... — Old Round- wood + 83... — ... — Hoy! and Silk- stone + 68... — ... — Williamthorpe + 60... — ... — Allerton Main + 50... — ... — NewHucknall 4- 25... — ... — North Gawber + 6... — ... — N e wm arket (Nelson) ... — 6 .. — — Barrow — 33... — ... — Wrenthorpe... — 73... — ... — Wooley — 88... — — Leighton — 90... — ... — Allerton By water - 99... — ... — §Sutton - 100... - ... — Elsecar Main - 108... — ... — §Teversal - 130... — ... — Warren House —150... — ... — Barlborough No. 2 -180... — ... — Parkhills — 257... — ... — Fence - 268 .. — ... — Orgreave - 273... — ... — Car House ... - 284.. — ... — Aston - 292... — ... — Langton ... — ... — Portland ... — ... — Barlborough No. 1 - 320... — ... — Seymour - 328... — ... — Pit. Height* Height.!^1; Ft. Ft. Ft.+ Norwood - 338... — ... — Ireland - 343... — ... — Waleswood ... - 350 . — ... — Whitwood - 350... — ... — AldwarkeMain - 350... — ... — Crigglestone.. — 357... — ... — Cortonwood... - 381... — ... — West Riding — 386... — — Wharncliffe Woodmoor - 394... — ... — Wombwell Main - 422 — ... — Roundwood... — 426... — ... — Carlton Main - 429... — ... — St. John’s - 434... — ... — West Kiveton - 436... - - ... — Tinsley Park - 448... — ... — Oxcroft - 456... — ... — Southgate — 460 .. — ... — Wheldale - 466... — ... — Bentinck ... — ■ ... — Fryston — 477... — ... — High Hazels... — 497... — ... — Kirkby - 547... h 556... 904 Glapwell — 582... — ... — Barnsley Main — 637... — ... — Whitwell - 640... + 120... 760 Glass Houghton — 643... — ... — MarkhamNo.l —701... — ... — West Sharlston — 710... — Monk Bretton — 714... — — Man vers Main — 764... — ... — Thrybergh Hall - 772 — ... — Snydale — 780... — ... — Mitchell’s Main — 796... — ... — * Ackton Hall... —819... — ... — Featherstone Main - 824... — — Treeton - 824... — — New Oaks — 837... — ... — Bolsover - 838... — ... — Kiveton Park — 900... — ... — Palterton — 900... — . — Sherwood — 900... •+ 138...1,138 Darfield Main — 902 — ... — Wath Main ... — 962... — ... — Pit. Height* Height.! 6DC6.J Ft. Ft. Ft. Creswell —1,035...+ 50...1,085 Pleasley -1 043...+ 346 1,389 Prince of Wales — 1,075.. — ... — Rotherham Main —1,165... — ... — Monkton Main -1,18.9... — ... — Mansfield —1,241...— 83...1,158 §Ackworth —1,250... — ... — Denaby Main —1,273... — ... — Shirebrook ... —1,289...+ 143...1,432 Rufford -1,335...- 250...1,085 Warsop Main - 1,339...+ 22 . 1,361 Langwith —1,339...+ 55...1,394 Shireoaks —1,370...— 64...1,306 §Barmborough —1,400... — ... — Hickle ton Main —1,437... — ... — Houghton Main —1,449... — ... — Steetley —1,548...+ 41...1,589 §Clipstone —1,555...— 270... 1,285 Grimesthorpe — 1,583... — ... — Askern Main.. -1 624...+ 70...1,694 Hemsworth ... —1,620 — ... — Thurcroft —1,611... — ... — Brodsworth Main -1,654...- 61... 1,593 Dinnington ... —1,656... — ... — South Kirkby - 1,700... — ... — Bentley -1,847...- 500...1,347 §Welbeck -1,860...- 275...1,585 Frickley -1,895... - ... — Bullcroft Main -1,986...- 332 1,654 Manton -2,034...- 500...1/34 Cadeby Main -2,043... — ... — Maltby Main.. -2,194..+ 82...2,276 § W allingwells — 2,349... - 100... 2,249 §Hatfield Main — 2,400... - 1,083... 1,317 . §Cantley —2,458...— 980... 1,478 § Yorkshire Main -2,551...- 182...2,369 Rossington Main -2,582...- 525...2,057 Thorne -2,736...-1,518...1,218 Haxey (South Car) -3,115...-1,719...1,396 * Above or below sea level of the Barnsley bed. t Above or below sea level of base of permian. J Difference = thickness of coal measure., above Barnsley bed. § The depths given for the pits marked § are only approximate. In using the method of triangles for ascertaining the run of the contours from these 112 available spot-levels of the Barnsley bed, Limitations to the method are soon discovered, and one finds that only over relatively small districts (rarely much more than half a dozen miles across) do the groups of adjoining triangles appear to indicate an unchanging direction for the lines of strike. Ats already mentioned, the method is strictly applicable only when the condition, that over the area represented by each triangle the surface is a plane lying uniformly between the points represented by the three apices, is satisfied. If, then, instead of a plane, the surface on which three haphazard points are taken is really a part of a cylinder, a dome, or a basin, or, which is worse, is broken by one or more faults into a series of steps, the geometry of the plane which passes through the three points the positions of which are known will give a very incomplete, and possibly erroneous, representation of the real average conditions as they are within the area. Fortunately, a great deal of the area under discussion is exposed coal field, and strata quite conformable with the coal seams can be inspected at the surface of the ground. Moreover, the coal field is in course of active exploita- tion, and actual coal workings have proved the geometry of the coal measures over areas which form a very con- siderable proportion of the whole. Such mining informa- tion, as well as that obtained by the hammer and the clinometer of the geologist, enables us to check infer- ences obtained by the three-point method, and if it appears that the apices of particular triangles are ’ unfavourably placed, the contours which might seem to have been indicated within the area of any one of those triangles may be discarded. In the actual drawing of the contours of the Barnsley bed and Top Hard coal there has been no case which has necessitated total neglect of any triangle, and although a freer humouring and sketching in of the contour lines as they curve in and out among certain points which are disposed along the troughs and arches of known folds, or on opposite sides of well-proven faults, * From a paper read before the Midland Institute of Mining, Civil, and Mechanical Engineers. has been allowed than was necessary in representing the evenly-spaced contours of the base of the permian, the total amount of non-geometrical adjustment required has not been considerable. Viewing the contours as they appear, smoothed out, and spaced as evenly as possible according to the mining and other available geological information, it will be noted that within the area in question (so far as explora- tion concerning which the results have been made public has extended) the slope of the surface, although irregular, has always a component to the east. The shallower contours appear to follow the run of the coal outcrop with considerable closeness, but contours belonging to greater depths, although evidently having sympathy with the shallower ones, and bending round disturb- ances which have directions similar to those that affect the outcrop of coal, depart considerably from . exact parallelism with the direction of ’that outcrop. The wider separation of the contours in depth, as compared with those near the outcrop, is a striking feature of the map, and especially noticeable wherever the strike of the contours tends north-westwards. With respect to the courses of the. individual con- tours, a study of the map in association with the fore- going table provides the best available information, and the writer will only further discuss them in so far as the localities in which they change their directions give evidence of the amplitude and continuity of the dis- turbances due to the earth movements which have affected the field. It may be noted in passing that only in the district south of Chesterfield have the measures which carry the coal under discussion been hard enough to resist denudation sufficiently to bring the place of the contour of + 100 yds. beneath the present'surface of the ground. In studying disturbances the writer will begin with those which affect the country in the south. The more important of the disturbances in this southern district have axes ranging north-west and south-east. Southern- most among them is the Ripley syncline, the north- western end of which dies away before it reaches the line of outcrop of the Silkstone coal. The outlying patch of measures containing the Top Hard coal about Swan wick and Alfreton owes its preservation to its being down- folded as a shallow trough between bounding faults which define the north-eastern and also the south- western margins of the syncline. From Pinxton by Blackwell to Tibshelf, the outcrop of the Top Hard coal follows a sinuous course, and the beds dip eastwards very gently. Between Blackwell and Silver Hill, and about Sutton, the strike appears to bend a few points eastwards. This eastward swell, which might be termed the beginning of the Mansfield anticline, affects all contours down to -500 yds., and possibly —600 yds., carries each one successively farther eastwards of its average line, and accounts for the advantageous mining conditions which in recent years have been experienced at the great pits of Sher- wood, Mansfield, and Rufford.