410 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[DfiCKMBER, 



ficial, and tlie senseless, ns the l;idy of orienUil story wlio went to dis- 

 enrhaiit lier brothers, or Rinaklo of La GirusaUmme Libcrata in the 

 enchanted wood ; if he persevere, some circumstance or other will be 

 sure to turn up, wliicti will show tlie mad sayings of such a Quixote, 

 are not so mad as they appeared to be. 



Perhaps the fire at the Tower may be considered a fortunate cir- 

 cumstance, tliough it has destroyed many proud trophies of national 

 victory, since it has not only consumed an uglv inappropriate unfor- 

 tress-like edifice, with a vast store of wretched useless arms which it 

 is confessed were unfit for service, but has so harrowed up public at- 

 tention to the subject, that it may be doubted whether any more such 

 dangerous repositaries may be built for containing public records, 

 trophies, libraries, pictures, or curiosities. 



If our ideas did not " run " as D'-. Robison says, "in a tcoodtn train" 

 and so induce tlie designing of buildings upon false principles, per- 

 haps hardly such a thing as a combustible public building would exist. 

 The cupola of the Pantheon, Palladio's representrtion of the leputed 

 Temple of Vesta at Nismes, the Cathedral of Milan, the Church of 

 Batallia, Rosslyn Chapel, and the Kitchen of Glastonbury Abbey, 

 show buildings may be roofed not only incombustibly, but also with- 

 out loss of sectional space between a ceilijig and an outer covering — a 

 beauty which, though often discoursed upon, is but very rarely pro- 

 duced. 



At the present day it is scarcely necessary to notice how much 

 more handsome and architectural, are solid vaultings than flat com- 

 bnstible ceilings: neither in good construction nor fire-proof construc- 

 tion, is it likely that any thing so ugly and unarchitectural as a dome 

 rising cut of a flat ceiling could ever be found; nor is it now much 

 more necessary to show that all the generic beauties of pointed archi- 

 tecture, are the direct and necessary emanation of fire-proof construc- 

 tion, every form from the summit of the vaulting of a church to the 

 buttress feet, resulting from that masonic cunning which was put in 

 action throughout tlie work to make every stone press to its neigh- 

 bours, instead of suftijring any cross strain, and snapping beneath it 

 like modern flat stone lintels and architraves; the only parts which, in 

 pointed architecture, are ever found violating this principle, are the 

 ugly ill-formed combustible roofs with which so many ancient churches 

 are covered, and which frequently being heavy, ill-designed, and 

 badly put together, by counteracting the masonic skill contained iu 

 the walls, vaultings, and buttresses of such fabrics, cause nearly all the 

 ruin which such edifices suffer. The finest piece of middle-age car- 

 pentry does not contain a tithe of the skill possessed by the fiee- 

 mascns; the imitation of ancient carpentry, in modern architecture is 

 a positive vice; national edifices built without such carpentry would 

 be found, in the long run, cheapest. It is to be hoped that when the 

 London Guildhall shall be rendered safe, by the removal of its present 

 roofii:g, there will be no new introduction of a roof of wooden faggots 

 for the martyrdom of its marble monuments. 



Not only may all edifices be incombustibly vaulted to appear tole- 

 rable, but to be in the highest degree architectural, and with the addi- 

 tional beauty of colour : tor vaultings may be formed in mosaic of dift'e- 

 rent coloured bricks, in herring-bone, chequered, or in any other man- 

 ner: and indeed by covering over the centering with plaster of Paris, 

 and drawing upon it any patterns, devices, or figures, every kind of 

 pictorial representation may be made as it were in carpet-stitch, 

 needing no plastering, no extraneous application of colour, scarcely 

 any future repair, and requiring from time to time simply to be washed 

 clean; parts of such vaultings may be glazed, parts may be finished 

 with fine porcelain, and the whole may be heightened with unfading 

 fired gilding. In some cases, patterns may be formed in light and 

 shade by indentations in the bricks, or by sunk stippled-work ; in 

 others variety of colour may be produced by sunk indentations filled 

 up by cement, some bricks with one colour, and others with a different 

 'one ; in palaces iind the higher class of edifices, embossed work and 

 all these methods may be united to produce one rich eft'ect. To insure 

 security to such vaultings with the least possible material, and there- 

 fore to render them lighter, and consequently requiring less abutment, 

 to make them, if possible, moie secure, though of but an inconsider- 

 :ible thickness, in all cases each brick should be secured to its neigh- 

 bours by small copper pins or plugs, so that though any trifling settle- 

 ments should happen to any part of the vaulting, still no derangement 

 should occur, and no part of the vaulting should drop without either 

 breaking the bricks or snapping off the pins. By these means Mr. 

 Bartholomew would undertake to produce a fac-simile of the vaultings 

 of the Temple Church, which neither fire, water, nor air should 

 destroy. 



ON THE ECONOMY OF FUEL IN LOCOMOTIVES CONSE- 

 QUENT TO EXPANSION AS PRODUCED BY THE 

 COVER OF THE SLIDE VALVE. 



Sir — I am very sorry that your correspondent Mr. M. should have 

 found reasons for regretting any expressions of his October letter, and 

 I can assure him that he meets with my most sincere regard, for hav- 

 ing found them, so to moderate the tone of his communications, that 

 he places himself in a position in which he is much less likely to meet 

 with asperity. Mr. M. now acknowledges that he objected unjustly 

 to the equation given fur finding the area of the piston necessary for 

 any assigned degree of expansion: which acknowledgment is of the 

 more value, since if this equation bad been wrung the whole paper 

 would have fallen to the ground : and he also now acknowledges that 

 inconsequence of a misprint he was led into the dilemma of supposing 

 that the area of the piston was put equal to the pressure of the steam. 

 Having thus satisfied himself as to the accuracy of the main features 

 of the paper, he now addresses himself to the demonstration that some 

 functions of the question which I neglected as being of verv small 

 amount are actually so " ap|)reciable" that even at the expence of 

 very much complicating the analysis he would recommend their in- 

 troduction. In replying to this demonstration 1 would have been saved 

 all trouble had Mr. M. subjected all his objectioLS to as rigid a calcula- 

 tion, as he has the effect tlvat the waste space at either end of the 

 cylinder has on the area of the piston, he finds, he says, that the cor- 

 rection which he has introduced for the waste space makes a difference 

 betwixt my formula and his of ^ of one per cent, upon the whole area 

 of the piston ; now I have neither investigated whether Mr. M. has 

 correctly introduced into the formula the waste spice, nor have I gone 

 through the numerical computation, for if Mr. M. has no objections, I 

 am perfectly willing to take for granted that he is correct in both, and 

 shall seek to produce only his assertion that the correction amounts to 

 so much as | of one per cent, on the whole area of the piston, as my 

 defence for neglecting the effect of the waste space. — But although 

 Mr. M. has found the correction to be as stated above, I will at the 

 end of this letter throw out a hint which will enable him to reduce it 

 to much less than even what he has found it, to probably one hundredth 

 part of it. 



Mr. M. L-ext proceeds to persuade me that he understands the mode 

 of analysis it is necessary to follow in estimating the work performed 

 by an engine working expansively, but in persuading me to believe 

 this, he persuades himself that I did not understand what he meant, 

 and I must allow that that is not only very possible, but very probable; 

 for although I believe that I thoroughly understood his words, yet un- 

 less thev happened to express his meaning, I could hardly be expected 

 to reach it ; but inasmuch as after explanation it turns out that we both 

 meant exactly the same thing, I shall take it for granted that Mr. M. 

 thoroughly understands the mode of analysis it is necessary to follow 

 in estimating the work performed by an engine working expansively, 

 and proceed to the consideration of more important matters, namely, 

 what Mr. M. states to be the real point at issue, and that is whether 



the constant term {t) in the expression -J- — / faithfully represenis 



the negative part of the effect, or the resistance of the waste steam on 

 the back of the piston. Mr. M. states that I put (/) to express both 

 the lowest pressure of the waste steam in the cylinder and the mean 

 resistance of the waste steam ; now I most certainly never intended to 

 make (0 express two distinct quantities, and I h ive examined the 

 paper to see if I had stated any thing which could furnish grounds for 

 supposing I had done so, but I cannot find that I did ; for the satisfac- 

 tion of Mr. M., however, I shall state in words (although to a mathe- 

 matician I have always been in the habit of supposing the language of 

 analysis most precise,) that (/) is put to express the mean effect of the 

 waste steam. Mr. M. will perhaps now discover that the expression 



— - — / does not give too great a value by 3 or 4 lb. per square inch. 



Mr. M. was probably led to suppose that (0 was put to express the 

 lowest pressure .of the waste steam in the cylinder by the way in which 

 it is involved in the equation for finding the area of the piston, but if 

 he reconsiders that equation on the supposition that (/) expresses the 

 mean resistance, he will find the error thereby introduced to be very 

 small, and to be in the opposite direction from that produced by ne- 

 glecting the w'aste space at the end of the cylinder. 



Mr. M. in the next paragraph asserts that when the time given for 

 expansion is excessively short as it is in locomotives, the reduction of 

 temperature due to expansion is not sensibly affected by the heat of 

 ihe smoke bos, and ought therefore to be taken into account; but for 



