1840.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



207 



The follo^ving is an estimate of quantities and labour for a b-ton 

 block, of thirty-six cubic yards, using rnortar made of lime, saud and 

 puzzolana : — 



36 cubic yards of broken stone. 

 12 „ puzzolana. 



12 „ lime in paste. 



12 „ sand. 



1 day's labour for a master workman. 

 3 " „ three labourers. 



The cases used cost about one hundred dollars, and one will answer 

 for twenty blocks. 



The whole cost of making and laying this beton at Algiers is about 

 five dollars and seventy cents the cubic yard. 



Estimate of quantities and labour for a befon block of one hundred 

 and eighty-two cubic yards, sunk in a case with a tarred cloth bottom, 

 caulked, using mortar made of lime and puzzolana : — 

 182 cubic yards of broken stone. 

 91 „ puzzolana. 



45i „ lime in paste. 



1 master workman three days. 



2 labourers for three days. 



The construction and moving of the case cost about four hundred 

 dollars ; it can also be used twenty times. 



The caulking at the angles, the" cloth bottom and the removal of the 

 case, cost about one hundred and se\-enty dollars. 



The whole cost of making and laying this buton at Algiers, is esti- 

 mated to be about eight dollars and seventy-five cents the cubic yard. 



Colonel Eniry published a work in 1S31, containing many purely 

 theoretical views, and at the same time many useful suggestions, in 

 whicli he set forth, strongly, the inconveniences of the present system 

 of building stone work in the sea, and proposed as a substitute, blocks 

 made of beton. 



The blocks that he proposed were also of two kinds, one kind made 

 in the water, and the other on shore ; the first was to be built in a flat 

 bottomed case, and the other he proposed to transport to the place for 

 immersion ; a plan of doubtful success ; he proposed, too, that these 

 blocks, which were to be hexagonal prisms, should be laid regularly 

 one upon the other, which we regard as impossible. 



During the execution of the new system at Algiers, some engineers 

 thought the success of it veiy doubtful ; but the manner in which the 

 end of the mole stands, puts all doubt to rest. This work projects 

 into the sea towards the quarter whence the winds blow with most 

 violence, and it stands without having sustained the slightest injury 

 from the most furious tempests. Besides other unquestioned advan- 

 tages presented by the use of beton blocks instead of loose stone, the 

 difficulty is avoided of transporting the stone of the requisite size when 

 the quarries are remote. This consideration amounts sometimes to 

 an insuperable obstacle to the use of loose stone, while the beton can 

 be used any where. 



The Romans drew blocks of stone from Mount Circe to build the 

 port of Anxium, a distance of ten miles ; and the pontificial govern- 

 ment was obliged to abandon the port of Auzo in consequence of the 

 difficulty of finding a qunrry in the neighbourhood, that would furnish 

 proper stone to repair the jetties. 



The Italians generally practise a mixed system. They build the 

 foundation of loose stones, even in twenty or thirty feet water, and the 

 top of masonry. The masonry is constructed in staunch cases, floated 

 to tlie place required, and the workmen, secure from water, erect a 

 wall usually of undressed stone and hydraulic mortar. The cases are 

 thus sunk by degrees until they reach the loose stone. The details of 

 this process are described in Belidor's Hydraulic Architecture, in his 

 description of the manner in which the moles at Nice, Genoa and Na- 

 ples were constructed. 



The defects of this plan are very apparent ; the bottom of the case 

 rests upon an uneven and movable surface, and the consequence is, the 

 masonry cracks open in many places. Moles thus constructed are soon 

 destroyed; extensive repairs are required, which make it necessary to 

 be continually throwing in loose stone. This is exemplified in the 

 mole at Genoa, which shelters the harbour from the east winds, the 

 end of which constantly requires repair. 



When De Cessart projected his large conical cases, he was on the 

 eve of discovering the simple and ingenious plan just described for 

 establishing foundations ; the great error which was committed, and 

 which fully explained the difficulty encountered by so skilful an en- 

 gineer, was in supposing that a wooden structure, however substan- 

 tially constructed, could resist the action of the sea. Acting on this 

 principle, he filled his cases with small stones to keep them in place ; 

 the consequence was that when the action of the sea beat these cases 

 to pieces, the stones fell down and the whole fabric was swept away, 

 De Cessart should have considered the case as simply a temporary 



enclosure to build masonry in, which would be capable of resisting the 

 force acting against it after the cases were destroyed. If he had taken 

 up this idea, it would probably have led him to the use of beton for 

 filling his cases. Instead of making these cases as substantially as was 

 proposed, it would be sufficient to give them the form of a large cask 

 without a bottom, made with uprights and staves bound together by 

 iron chains instead of hoops, in sucli manner that the uprights can be 

 taken apart when the case is to be taken up. Another indispensable 

 condition is, that the case should be filled in the shortest possible time. 

 The sea at Algiers is very powerful considering the little range it has; 

 and it would be necessary to make such arrangements that a case made 

 to contain about 1300 cubic yards, should be filled in thirty-six, or 

 forty-eight hours. This might be done by throwing in beton blocks, 

 reaijymade, at the same time pouring in beton to bind them, by means 

 of cloth funnels fixed to the cases. This suggestion has never been 

 acted upon, but if the intention of making Algiers a military port be 

 carried out, there will be an opportunity of trying it on a large scale, 

 and it is believed with complete success. 



Whatever may be the fate of this or other plans for using beton, one 

 thing is certain, that sooner or later, the practice of making founda- 

 tions at sea with loose stone will be entirely abandoned, and masses of 

 the natural rock so costly in quarrying and transportation, and so in- 

 sufficient in dimensions, will be replaced by artificial blocks made of 

 beton. 



THE EFFECT OF CURVES ON RAILWAY CARRIAGES. 



Sir — The influence of railway curves on engines and carriages passing 

 along them, appears to have been paid little attention to by those. 

 persons who have had the best opportunities of acquiring information 

 on the subject ; at least, I am not aware that the results of any obser- 

 vations on the subject have been made known to the world. The only 

 remark bearing on the matter which I have seen published, is contained 

 in a letter by Mr. J. Ely, at page 139, vol. 2, of your Journal, in which 

 he assei-ts "that when an engine is entering upon a curve, it will be 

 affected by the nature of the path it was previously describing, and 

 that the wear ami tear of the onUr rail at the commencement of a 

 sharp cur\e is ?tso when the previous jiath is a curve in an opposite 

 direction (forming an S), than when it is a straight line." I do not 

 for a minute doubt the correctness of the latter part of his assertion, 

 but think that the inference he would draw from it, that an S curve 

 is preferable to a straight line connected with a single curve, is erro- 

 neous. If you consider the subject, you will instantly perceive that 

 the outer rail at the commtnceiiuiit of a reversed curve, would scarcely 

 be aftected bv the grinding of the vv-heels, but that the inner rail would 

 have all the wear and tear which is, simply, not from tl.e engine or 

 carriages being influenced by the path they were previously describing, 

 in the sense which he applies it, but from the centrifugal power 

 throwing the carriages against the outer rail of a curve, and which, at 

 the point where the curve is reversed, has not had time to be counter- 

 acted, and which will not be the case until the carriages have passed 

 a considerable distance into the second or contrary curve, when the 

 wheels will begin to grind the outer rail of this curve as they did that 

 of the preceding. My principal reason for addressing you is to draw 

 attention to the great wear and tear of engines and carriages caused 

 by their traversing curves, and to induce an inquiry into the subject, 

 for the purpose, if possible, of modifying the evil. My opinion on 

 the matter is, that any engine or carriage, in traversing a curve, under- 

 goes a degree of torsion in the framing, and thereby partially adapts 

 itself to the path which it is traversing, and which, with a slight de- 

 gree of sliding of the wheels on one side, enables it to pass along the 

 line without such a vast increase of friction as might reasonably be 

 inferred. Now if such is the case, and a carriage is drawn or propelled 

 along an S curve, the extremes of torsion will almost instantly take 

 place where the two curves join, the framing being then twisted in 

 the contrary direction, and the destruction of carriages must be cora- 

 niensuratelv great with the suddenness or violence with which the 

 change is effected. I would therefore offer, as a partial remedy, the 

 laying in of a short tangent line to the two curves in every instance, 

 instead of an S curve, whereby the extremes of torsion, in place of 

 being sudden, and I presume 'destructive, as in the latter, would be 

 gradually effected, first by the restoration of the framing to its square 

 form, and then by the slight torsion in the contrary direction. If this 

 plan was pursued, I have no doubt very much greater durability in the 

 engines and carriages would be the consequence. Perhaps some of 

 your readers who have opportunities of minutely observing the effects 

 which I have described, and also the effect where sharp curves are 

 connected with a tangent, will, at some future time, communicate the 

 results. 



June, 1340. B. 



