270 THE BUILDING NEWS. Apri 5, 1872.
The dimensions of the specimens to which the tests were applied were 3-96 x 1:98in. = base area 7-84in. The pairs of bricks bedded together and pulled apart gave the following results. Area of joint 18-5 square inches :— COMMON MORTAR. Highest Lowest Mean of stress, stress. 3 tests. Ib. lb. Ib. 1to3of sand... 207 144 166 sie) asst eee A OT, 121 154 SE oie acs 145 104 LAT PATENT SELENITIC. Lt;, Sea vente G0 322 353 ey iO wadieese | OUI 287 329 OKs 326 149 243 Tests for pulling stress; dimensions of spe- cimens 2-*5in. X 2:0 = sectional area 5-0 Square inches. COMMON MORTAR GAUGED. Highest Lowest Mean of stress. stress. 3 tests. lb. lb. lb. Dtodof sand... 169. ..@ 123 150 Lae ey OP aes 104 116 Paes gee 71 88 PATENT SELENITIC GAUGED. PPARs es Vy '892 395 360 eT Outs th tr ose 380 342 360 Line. 289 202 233 PATENT SELENITIC PRESSED. AA a) SAR, 381 433 Tio =the AROS A738 403 431 ab ve eee eth 498) 326 380 The following may be taken asa mean aggregate summary of the different classes of tests :—Thrusting stress : Common mortar, 1 of lime to 3 of sand; mean resistance, 9541b., or per square inch of area, 121-7lb. Patent selenitic mortar, 1 of lime to 5 of sand ; mean resistance, 2,236lb., and “ pressed,” 4,936lb., or 284°5 and 629-6 per Square inch respectively. Tests of pulling bedded bricks apart: Common mortar, 1 to 3, mean resistance, 1421b. ; selenitic, 1 to 5; mean resistance, 338lb., or 7:67 and 16-65 per square inch respectively. Tests for pulling specimens asunder: Common mortar, 1 to 5; mean resistance, 118lb.; _ selenitic, 1 to 5; mean resistance, 318lb ; and the same “ pressed,” 415lb., or upon the square inch, 25°6, 63°6, and 83-0 respectively. Tt is stated that Lee’s Burham, Barrow, and Dorking gray limes are equally well suited for the selenitic process. ——_——_ > NOTES ON EARTHWORK.—II. Bs considering how to present the subject in the best form and in logical sequence, it seems that the best way willbe to treat the subject under the heads of the different classes of work—yviz., railways, waterworks, sewers, roads, and other works, because the means, appliances, and methods which are suitable to one of these are different from those which are suitable to the others. It might haye been arranged under the heads of the different kinds of work, let them be per- formed where they may; such, fur instance, as (1) stripping off the top soil, but this does not apply to any great extent in sewage ; or (2) excavating earth and depositing it in embankments, but the mode of forming em- bankments for railways and for waterworks’ reservoirs is so essentially different that that would not seem to form an intelligible head under which to treat the subject; and in sewer work the earth excavated is replaced in the trenches ; and, in short, it appears more de- sirable to pursue the subject under the heads first named. But before proceeding to them— the three former of which are chiefly works of the last forty years—we may remark that the earliest earthworks of modern times—exclud- ing, that is to say, the works of the Romans in this country, which were chiefly for military purposes—were the drainage of the
fens of Lincolnshire, Cambridgeshire, and Huntingdon. The churchmen of the Middle Ages were the first to cut drains in the fens on a large seale, but on the dissolution of the monasteries the banks were neglected, the rivers were allowed to silt up, and the fen lands were again covered with water. But about 250 years ago the drainage of the fens wasrevived. Cornelius Vermuyden (according to Smiles’s ‘ Lives of the Engineers”), a Dutch engineer, accustomed to similar works in his own country, was invited over by the proprietors of the fen lands of Lincolnshire, Cambridgeshire, Huntingdonshire, and Nor- folk, and in the course of some twenty-five years he drained the greater part of the fens. Some of his cuts were very large. The Old Bedford River was 70ft. wide and _21 miles in length. Bevill’s Seam was made 40ft. wide and 10 miles long. Sam’s Cut 20ft. wide, 6 mileslong. Sandy’s Cut 40ft. wide, 2 miles long. The New Bedford River was 100ft. wide, diverting the course of the river Ouse from its former length of 40 miles to one of 20 miles in a more direct line. S. John’s River 120ft. wide, 10ft. deep, from Denver Sluice to Stow Bridge on the river Ouse. But in these works of Vermuyden an important error was made. They formed, in- deed, so many receptables for the water which drained from the land, but their outfalls to the sea were made at too high a level, and, consequently, after long periods of rainfall they overflowed the land. Im the Great Bed- ford level the water so frequently took pos- session of the land that the fen men called it the bailiff of Bedford.
Tt was not until about 70 yearsago that the true principle of drainage of the fens was adopted by Mr. John Rennie, the eminent engineer, the two great features of whose plan were (1) intercepting the flow of water from the higher lands on to the lower or flat lands, by cutting catchwater drains all around the margin of the fens, and carrying away the water so caught direct to the sea or to a tidal river ; and (2) cutting down the outfalls of the main drains or rivers to the lowest possible level of low water at the outfall. In this way he most successfully drained the east and west fens and the Wildmore fens of Lincoln- shire, and in the course of seven or eight years Mr. Rennie cut 100 miles of drains. The main drain through the Wildmore and West fens to the river Witham was 21 miles in length, and 30ft. wide at its lower end, diminishing upwards. The bottom was formed with a uniform inclination of 6in. per mile. For the East fen the main drain was 18 miles long, 40ft. wide at its lower end, and diminishing upwards. The inclination is 4in. per mile. ‘The catchwater drains varied in bottom width from 16ft to 6ft. he length of drains cut in the seven or eight years during which the works were in progress was about 100 miles. This principle was adopted by Rennie in other places, and has continued to be adopted by other engineers to the pre- sent day. Most of these main drains or arti- ficial rivers serve two purposes, the one to drain the land and the other to offer a means of transit for merchandise and agricultural produce.
The first navigable canal in England—that is to say, a canal cut for the sole purpose of the transport of merchandise and produce— - was made about 110 years ago by James Brindley, for the Duke of Bridgwater, from Worsley to Manchester, followed quickly by an extension to Runcorn, on the Mersey, and from that time until railways began to be made, forty years ago, a vast deal of earth- work was performed in making canal navi- gations. Brindley alone made 365 miles of canalin about twelve years. After Brindley had shown the practicability of making water- tight channels through any kind of ground whatever, and even on earth embankments, by means of puddled clay, the rapidity with which canals were made resembled that with which railways were constructed after George Stephenson had shown on the Liverpool and Manchester Railway that locomotive engines could take passengers at a faster rate of travelling than the best stage-coach had done. According to Mr. Smiles (‘‘Lives of the Engineers”), there have been made in Eng- land 2,600 miles of navigable canal, in Ire- land 276, and in Scotland 225 miles, the cost of which was about 50 millions of money, and there was nota place in England south of Durham more than fifteen miles from water communication. Brindley’s canal embank- ment across Stretford meadows, near Man- chester, was 900 yards in length (more than half a mile), 112ft. wide at the base, and 24ft. wide at the top, the height being 17ft. As James Brindley made the first of a long series of navigable canals in England, so John Metcalf made the first of a long series of roads, about one hundred years ago, from Harrogate to Knaresborough, in Yorkshire. One of the first roads he made was laid out across a bog, and the manner in which he carried the road over it was precisely on the same principle which George Stephenson adopted sixty years afterwards in carrying the Liverpool and Manchester railway over Chat-Moss—yiz., to diminish the weight placed upon a weak foundation, and at the same time to increase the bearing surface sup- porting the load. This he accomplished by placing ling and heather, gathered from the adjoining ground, and bound together in little round bundles, first lengthwise of the road, the bundles being laid close together; and, secondly, similar bundles laid across the first layer; and upon this foundation the road stone was laid. He took the precaution also to cut a drain on each side of the line of road, and with the materials to raise the road bed above the water level. Upon this light bank of peat the bundles of ling and heather were laid. Roads continued to be made pari passu with canals until about forty years ago. About that time a great road leading from London to the north of England was laid out by Tel- ford, the engineer, but before anything further was done in the matter, George Stephenson had demonstrated the superiority of railways, and the project was abandoned. The first thing to be done in making a rail- way is to set out the centre line, and driye stakes into the ground at equal intervals of a chain, or of 100ft. apart. Where the line is straight, it can be ranged with poles alone, if the distance is not great; but, in general, straight lines as well as curves are ranged with the theodolite. A curve may be set out by perpendicular offsets from the tangent line: thas, in Fig 1, let R be the radius of the curve, a6 the tangent line to the curve at the point a, O the perpendicular offset at any given distance T, then— : o=R-— VR—T. Thus, if the radius be 20 and the tangent 10, 20 — ¥ 20% — 10? = 20 — 17°32 = 2°68, the offset, in feet, if the other dimensions are taken in feet, or generally in the terms of the other dimensions, Accordingly—
