380 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[December, 



quantity of material. And one of the results deducible from the experi- 

 ments instituted by the late Lieut. Hope, at Chatham, is in favour of the 

 " leaning wall wilU counterforts." Lieut. Hope "conceived that the face 

 of the revetment might be a mere shell, hardly exposed to any pressure, 

 the earth being chietly supported by its friction against the sides of thin 

 but frequent counterforts." 



" These results cannot, however, be admitted as conclusive against the 

 several other forms which have been, in some instances, adopted. Thus 

 the second form appears well adapted for stability, and has the advantage 

 of an enlarged section below, and a reduced one above, from the same 

 amount of materials as No. 5. Again, the third form appears to be very 

 strong, and well adapted to escape injury from any extra pressure result- 

 ing from the absorption of water by the retained bank. 



" But it must be observed of the first, second, and third sections, that 

 the inner face of all of them departs more widely from the natural slope 

 of the earth, and therefore sustains a greater pressure than the inner face 

 of section No. 5. Section No. 1 is evidently inferior, by reason of its 

 uniform thickness, which must be either excessive at the upper, or de- 

 ficient at the lower part of the wall. The defect of uniform thickness 

 is parly compensated iu No. 5 by its inclined position, which gives it a 

 tendency to fall back upon the earth, and thus resist its pressure. 



" The value of this fifth form of retaining wall appears to arise from the 

 line of direction being thrown beyond the centre of the base, thus giving 

 a preponderating weight within this line, the efl'ect of which weight in- 

 creases in proportion to the height of the wall and its divergence from 

 the perpendicular. The angle of this divergence remaining the same, 

 the height maybe supposed to be reduced till the line of direction falls 

 within the base, and the active weight of the wall becomes reduced to 

 nothing ; or, on the other hand, the height may be supposed to be in- 

 creased until this active weight shall equal any pressure of the retained 

 earth. And this consideration will, perhaps, partly account for some of 

 those instances of movement in the middle or upper part of retaining walls 

 thus formed, which are well known in practice, and which we have 

 already had occasion to notice. In these cases we may imagine, that un- 

 less the construction of the wall is such as to insure a superior cohesion 

 among its parts, the upper part of the wall will have a tendency to fall 

 backward, while the lower part (of which the line of direction falls with- 

 in its base) will have no such tendency. The upper part, obeying this 

 tendency, becomes dislocated from the lower, and will be forced forward 

 by the pressure beyond it. 



"The great importance, in works of this class, of judicious construc- 

 tion, not only in design, but also in practical execution, will justify 

 the introduction of a few hints upon brick-work and bonding generally, 

 especially as iu all cousiderations upon those works we have to assume 

 the perfect cohesion aud entire rigidity of their parts ; and our conclu- 

 sions will, therefore, be more fallacious in proportion as these conditions 

 are neglected and non-realized in practice. 



" In the first place, the arrangements of the bricks should be that 

 known as English bond ; viz., one course of headers and one of stretchers 

 alternately. The bonding of the plain part of the wall should be 

 secured by introducing a half brick for every alternate outside header 

 on both sides of the wall, so as to connect the outside headers with the 

 bricks in the interior of the same course. At every fourth course, or 

 thereabouts, three or four bands of iron hooping, laid parallel, and bedded 

 in the joints, assist the bond. At each returning wall or counterfort, 

 quarter bricks are required, in order to avoid straight joints on the face 

 of the wall, and preserve the bonding at these angles. In all battering 

 walls it is especially necessary to insist upon narrow joints perfectly 

 filled with mortar, and truly pointed. This is the only means of guard- 

 ing against, or rather deferring, that penetration by wet and frost which 

 is so detrimental to the stability of the work. The bricks, too, should 

 be thoroughly wetted before and during the setting, so as to detect any 

 injurious quantity of limestone which may exist within them, aud also to 

 cleanse them and render the mortar thoroughly adhesive. In all cases 

 the work should be brought forward simultaneously, or as nearly so as 

 possible, throughout the whole length in hand, otherwise the shrinkage 

 which invariably occurs will be unequal, and produce internal dislocations 

 of the wall, which will accelerate, if not produce, ultimate failure. Simi- 

 larly, all counterforts must be erected along with the wall itself, for all 

 subsequent connections of these parts will be necessarily imperfect. 



" The concrete and lower courses of brick-work or footings should be 

 deeply notched into the solid ground on the inner side of the wall. If 

 this be carefully observed, and all spaces in the excavation or trench cut 

 for putting in the foundations be well rammed, no movement of the 

 foundations can take place without it be actually lifted to the extent of its 

 entire depth, or without crushing the solid ground before it. in a simi- 

 lar manner, all the courses of bnck-work should have a dip downwards 

 from the outside face of the wall, and, in short, every possible means be 

 adapted of connecting the entire mass of wall and foundations indisso- 

 lubly together. 



'■ All reductions in thickness should be made in steps, keeping the 

 intermediate sections of the wall parallel ; for if any attempt be made to 

 reduce by tapering lines, the restriction to proper sized bricks and parts 

 of bricks is necessarily disregarded : bats, and pieces of every variety, 

 size, and shape, are thrust in, so as to preserve the outside lines only ; 

 and good bonding and narrrow joints are alike unheeded. And this 

 ms a great practical superiority of the fifth form of wall over the 



second, third, and fourth. The fourth section, indeed, is otherwise so 

 objectionable, that it can be selected only under tlie absolute necessity 

 of preserving a vertical face, and a back inclined towards the natural 

 slope of the retained earth. 



" A practical rule for a section of retaining wall which has in many 

 cases proved sufficient, and has yet been deemed economical, is as 

 follows : — let the batter equal one-sixth of the vertical height of the 

 wall; the thickness of wall at the bottom equal one-fifth of this height, 

 and the thickness at top one-tenth the height, or one-half the thickness at 

 bottom : and for the reducing of the thickness, divide the entire height 

 into as many equal parts, plus one, as there are half bricks in the ditier- 

 ence between top and bottom thickness. Thus a wall 30 feet high will 

 batter 5 feet, be 6 foot thick |at bottom, 3 feet at top, and be divided 

 into nine different thicknesses, each 4^ inches less than the lower ad- 

 joining one, and each 3 feet 4 inches in height, measured vertically. 

 Under ordinary circumstances, however, economy of material may per- 

 hops be effected, or greater stability be secured, by reducing this thick- 

 ness, and introducing small counterforts at frequent intervals." 



Average Items of the Construction of a Mile Railway, 



" The average quantities, per mile, of the several items which are in- 

 volved in the formation of a double line of railway, of the 4 ft. 8J in. 

 gauge, up to the completion of the permanent way, and exclusive of the 

 stations and buildings, and locomotive and carrying stock, may be com- 

 puted as follows : — 



" The quantity of excavations in 342 miles of double line of railway 

 (comprised in ten railways) amounted to 35,338,000 cubic yards, giving 

 an average of about 103,330 yards per mile, or 58 71 cubic yards of earth- 

 work for each yard forward of the line. Assuming the width of the 

 formation level to be 10 yards, or 30 feet (which is about the average), 

 with an additional width of 5 yards on each side, for ditches, hedges, is.c., 

 the slopes at IJ base to 1 of height. — and also assuming the whole line 

 to be, either in cutting or embankment, of an average depth of height of 

 H feet, — we shall require 5(i73 cubic yards of earth-work per yard 

 forward of the line. This is sufficiently near to the actual average of 

 68"71 yards ta answer the purpose of this general calculation. The average 

 width of land required will thus be 

 Central width Base of Slopes. Ditclies, &c. 



I « , r^ -i*-\ 



30 -f- lG-5 + 16-5 -f 15 -f 15 = 93 feet, or 31 yards, 

 which will give about 11 J acres of land per mile. Allowing for severance, 

 iec. this may be assumed at 12 acre. 



" The quantity of ballasting 30 feet wide, and 18 inches thick, will 

 equal 5 cubic yards per yard forward, or 8800 cubic yards per mile. 



" The sleepers, transverse, 8 feet long, and 10 inches by 5 inches, 

 placed 2 feet 6 inches apart, will require 11,733 cubic feet, or 235 loads 

 of timber; or 4224 sleepers per mile. 



" The chairs required, supposing the rails to be rolled in lengths of 

 15 feet each, will be 1408 joint chairs, and 7040 intermediate ; and their 

 weight, reckoning each joint chair at 20 lbs., and each intermediate chair 

 at 15 lb., will be 12 tons 11 cwt. 1 qr. 20 lb., and 47 tons 2 cwt. 3qrs. 

 12 lb., respectively, or 59 tons 14 cwt. 1 qr. 4 lbs. together. 



" The rails, assuming the weight at 5B lb. per yard, will weigh 176 

 tons, — 1408 lengths being required. 



"If two oak trenails and two iron spikes be required for each chair, 

 16,896 of each will be wanted per mile, with 8448 wooden keys for fix- 

 ing the rails in the chairs. 



" If felt be interposed between the chairs and sleepers, and the former 

 be assumed at 10 X 5 inches bearing surface, 2933 square feet of felt 

 will be required per mile. 



" The timber in the side fences, formed of posts 8 feet long, 6x4 

 inches, 9 feet apart, with four rails 5 x 2i inches, and intermediate up- 

 right stay 3x2 inches, will consume as follows : 1174 posts = 1565 

 cubic feet; 4696 fails = 3666 cubic feet; 1174 stays = 269 cubic feet; 

 or a total of 110 load 



" Of the masonry, timber, iron, &c., &c., in bridges, viaducts, culverts, 

 drains, retaining walls, &c., scarcely any estimate can be formed. Taking 

 the average of a few cases, the masonry would appear to amount to about 

 110,000 cubic feet per mile ; but in some cases from 30 to 50 per cent, 

 of this quanlity is substituted by timber and iron." 



Railways made of wooil were first used in Northumberland about the year 

 IR.'i.S, and made of iron at Wtiitehaven In 17;W. The lirst iron railroad was laid down at 

 Colbrook-dale in ITBS. Steam power to convey coals on a railwiiy was first employed liy 

 Blenkinsop, at Hunslet, near Leeds, and alterwards on the Stockton and Darlington 

 Railway. 



The iliaught of water of the respective brigs composing the Experimenfal 

 Squadron on their arrival at Plymouth Sound, Dec. 6, IS44: — 



Forward. Aft. 



Osprey llft.Sin 15 ft. in. 



FlyinnFish 13 14 7 



Espiegle 12 6 14 8 



Mutine 12 2 13 ID 



Daring It 8J 16 7 



Cruizer 12 2 14 6 



Waterwitch 10 3 14 9 



Pantaloon 11 6 13 5 



