348 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[October, 



PROCEE3JKGS OP SCIENTIFIC SOCIETIES 



INSTITUTION OF CIVIL ENGINEERS. 

 April 11. — Joshua Field, V.P., in the Chair. — (cantinued.J 

 Screw Cutting. 



Some specimens were exhibited of screws cut in lathes constructed by 

 Messrs. Shanks and Co., of Johnstone, near Paisley. They were sent by the 

 late Sir John Robison, who described the principal advantages of the ar- 

 rangement of the lathe for cutting them to consist in the cutters acting 

 during the incursion as well as the excursion of the slide, and when forming 

 long screws, in their being alternately stayed on the side opposite to the too! 

 which was in action ; that by these means, good work could be produced 

 with such dispatch, as to reduce the cost of turned screw bolts, as low as 

 that of similar articles produced by screwing machines, which worked with 

 dies acting by compression. 



A drawing of the lathe used in cutting the screws was presented with the 

 specimens. 



Mr. Field observed that the machine was ingenious and appeared to do 

 the work well; but as far as could be ascertained from the drawing there 

 was not any novelty in it. A similar machine made by the late Mr. Mauds- 

 lay, had been in use in Maudslay and Field's manufactory for the last 15 

 years. The screwing dies invented by Mr. Whitworth, cut out the threads 

 of screws as clearly as if done by a chasing tool, and entirely without com- 

 pression. 



April 25 and May 2. — The President in the Chair. 



" An Account nf the Brick-making at Blechingley Tunnel, during the 

 whiter of 1840 and summer of IS 11." Bv Frederick Walter Simms. M. 

 Inst. C. E. 



As the forming of this part of the Dover Railway was not let by contract, 

 it was necessary to make extensive preparations previously to commencing 

 the work, and amongst these the brick-making department was one of the 

 principal, the whole being under the personal superintendence of the author. 

 The bricks were all made on the surface along the line of the tunnel, the 

 brick-grounds being so arranged on each side of the shafts, that when the 

 bricks were delivered from the kilns and stacked, but little labour was neces- 

 sary to convey them to the spot, whence they were lowered to the under- 

 ground works. The mode of manufacture adopted was that of " slop- 

 moulding," in which process the mould is dipped into water previous to its 

 receiving the clay, instead of its being sanded as is the case in making 

 sandstock bricks; the workman then throws the clay with some force into 

 the mould, pressing it down with his hands to fill all the cavities, and strikes 

 off the overplus with a stick ; an attendant boy, who has previously placed 

 another mould in a water trough by the side of the moulding tabic takes 

 the mould just tilled, and carries it to the floor, wnere he carefully drops the 

 brick from the mould on its flat side and leaves it to dry; by the lime he 

 has returned to the moulding table and deposited the empty mould in the 

 water trough, the brick-maker will have filled the other mould, for the boy 

 to convey to the floor where they are allowed to dry, and are then stacked 

 in readiness for being burned in clamps or kilns. Minute details of the 

 manufacture are then given, the average results of which arc shown in the 

 following table : — 



A careful comparison is then made between the two nodes of sandstock 

 and slop-moulding, from which it appears that while the production of sand- 

 stocks is as 30 to 1G of the slop process, the amoi:nt of labour is as 7 to 4, 

 and that the quantity of land required and the cost of labour per thousand 

 are nearly the same in both processes. The bricks were all burned in close 

 kilns constructed with soft bricks set in pugged clay, the quantity burned in 

 them at a time varyiag from 30,000 to 40,000. The fuel employed was that 

 known by the name of the Bell Robson Netherton, or South Hartley coais, 

 and for the purpose of more accurately determining the cost of this ele- 

 ment, the author caused the quantity of coais consumed in burning °4 kilns 

 of bricks to be carefully noted : this is given in a table accompanying the 

 communication; the average of it is, that 10 cwt. S lb. of coal were used. 



in burning each thousand of bricks. The floor of the drying-houses was 

 made of pugged clay about nine inches thick at the furnace end, and gra- 

 dually diminishing to two inches at the extreme or chimney end, so as to 

 equalize the heat of the floor. The temperature of the interior of these 

 drying-houses when in full operation varied from 50' to 70° Fahrenheit. 

 The estimated cost of the bricks delivered at the shafts was 2?. Is. lOd. per 

 thousand ; but the actual cost, obtained by dividing the total expenditure by 

 the whole number of bricks made, was only 11. Is. 6d. per thousand, which 

 includes waste and all other expenses that were incurred. 



The author notices the substitution of Mauritius sugar mats for the ordi- 

 nary hack-caps made of straw, and that they were durable and serviceable. 



The paper is accompanied by two drawings showing the elevations and 

 sections of the kilns and drying-houses with their flues. 



Remarks. — In answer to questions from several members, Mr. Simms 

 stated that the price of moulding bricks by the slop process was 5s. per 

 1000; that slop bricks occupied less time in drying than sandstock bricks; 

 that the former kind were full one pound each heavier than the latter, which 

 he attributed to the greater amount of pressure they received when being 

 moulded ; for this reason also the sandstocks were made somewhat quicker. 

 The price of the ordinary hack-caps made of straw was 4d. each, and they 

 lasted one season ; the Mauritius sugar mats which were substituted for 

 them, cost about Id. each and would last two seasons. 



Mr. Bennett thought that the quantity of bricks which could be produced 

 by each gang of men was under-rated, for, at Cowley, the average number of 

 sandstocks moulded was 32,000 per week ; while his men very frequently 

 made 37,000, and sometimes they reached as far as 50,000. The space oc- 

 cupied for moulding at Blechingly appeared small; in Mr. Bennett's brick- 

 ground 10 stools occupied 20 acres ; this might arise in some degree from 

 more time being allowed for drying in the sandstock process : he believed 

 this to be an advantage; the principal part of the shrinkage took place 

 while drying previously to being burnt. The total amount of contraction in 

 his bricks was ±$ inch in 10 inches; but all clays differed in the amount of 

 contraction. 



Mr. Farey directed the attention of the meeting to Hunt's improvements 

 on the Marquess of Twceddale's machine for making bricks ; it had not, he 

 believed, yet been brought into general use in England, but it was em- 

 ployed extensively at Hamburgh and other places on the continent, and was 

 stati .1 to produce stronger and better shaped bricks, of more uniform quality 

 than those made by hand moulding ; the process was a kind of intermediate 

 one between slop and sand-moulding; the moulds being wetted as in the 

 former process, while the clay was tempered in a pug-mill as in the latter 

 process. 



A very ingenious system of moulding without wetting the clay had re- 

 cently bee:; introduced by Mr. Prosser of Birmingham. At present the 

 system was confined to the production of buttons, small tiles, and slabs for 

 painting; but the patentee asserted that the machine could he advan- 

 tageously used in making bricks. A few had been made which in burning 

 only shrunk j^tb of an inch in inches. 



Mr. Bennett said the Marquess of Twceddale's machine hail not been 

 adopted generally, because of the first cost, and that the necessity for em- 

 ploying horse power, or a steam-engine, for working them, rendered the 

 bricks more expensive than when made by hand. 



Mr. Ilomersham stated that steam or horse-power was not indispensable; 

 that Messrs. Simpson and Co. had made several of Hunt's machines for the 

 Tweeddale Brick Company to be worked by manual labour, and that they 

 succeeded perfectly. He found the bricks so produced about one-sixth 

 stronger than those made by band, which he attributed to the degree of 

 pressure to which they were subjected. 



Mr. Simms objected to the use of machinery chiefly because it would 

 only effect an economy in the moulding, which was but a small part (about 

 one-eighth) of the expense of making bricks. 



The contraction of the bricks varied according to the nature of the clay 

 employed ; the moulds used at Blechingley were 10 inches long by 5 inches 

 wide and 3 inches thick, and the bricks when burned were 9 inches long by 

 4J inches wide and 2^ inches thick. The chemical constitution of different 

 clays, and the relative proportions of alumine and silcx contained in them, 

 would be a subject of much interest and practical utility, to be brought 

 before the Institution by some member possessing the necessary chemical 

 knowledge. 



Mr. Bennett mentioned the existence of a brick machine invented by Mr. 

 Ainslie, and now working in Scotland ; it was, he believed, somewhat cum- 

 brous, and required to be driven by steam power, but he had understood 

 that it produced very good bricks and tiles, but was chiefly employed to 

 make the latter. 



In answer to a question from the President, Mr. Simms said that the 

 bricks at Blechingley had been made without any cavity in the top and 

 bottom, in order not to waste the cement in which they were laid. En- 

 gineers entertained very opposite opinions as to the utility of the cavity in 

 the bricks. 



Mr. Cubitt preferred the bricks having a cavity, if they were to be laid in 

 mortar; with cement it was of less importance. 



Mr. Farey believed that when the cement was stronger than the bricks, 



