140 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[April, 



A PRACTICAL METHOD OF SETTING OUT A CIRCULAR 

 RAILWAY CURVE, 



WITHOUT THE USE OF ANY INSTRUMENT FOR TAKING ANGLES. 



Let A be tlic commencement of a ciicuhir curve: perpendicular to the 

 radius AO measure any distanct! AT, and from ii tlie middle of AT measure 

 nm equal to An or »i T meeting Tm = .J T"- -^ y^ aT=~+2X0 = , then will 

 m be a point in the curve. Ag.iin, measure in the direction of w m' to T' 

 making- m T' = AT, and from T' the middle of mT measure /I'm'^ii'T', or 

 n'm meeting Tm' = T»i, then will )»' be another point in the curve, and tlius 

 any number of equidistant points may be found. 



Demonstration.— Becaus e T)H X B T — A T-, and TB= = AT2+2AO', 

 we have Tm = AT= -^ -j/ AT'^ +2 A 6% then will m be a point in the 

 curve. Again, join O HI and A 01, then since T />=:/( i.'i^n A, the point n 

 is the centre of a circle passing through A, m, T ; therefore Am is perpendi- 

 cular to T)», and nm a tangent to the curve at in. 



The method of proceeding on the concave side of the curve is equally easy, 

 and depends on the same geome;rical principles. The foregoing supersedes 

 the necessity of taking any angles. The methods given for laying out curves 

 in the March and preceding " Railway Magazines," though founded on true 

 principles, require either a theodolite or a table of sines and tangents, while 

 this method requires neither, and appears simpler and more fitted for practice 

 tlian any I have seen. 



HLSTORY OF PAPERHANGINGS. 



E.rtracts from a paper by Mr. Cr.vce, read before the Royal Institute 

 of British Architects. 



(Continued from page 100.) 



In the former paper I endeavoured to trace the history of the art of 

 paperstauiing up to the present time, and it is no\v my purpose to describe 

 the manufacture, and give some account of the modern improvements that 

 have been introduced. 



In that paper I showed, I trust satisfactorily, that tlie flock papers, or 

 rather liangings, were introduced into England in the time of Charles I., 

 hikI that a person named John Lanyer obtained a patent for the invention 

 in 1G.34. I also cited an article from an old French dictionary of com- 

 merce, pro\ing that the coloured paperhangings were made at any rate in 

 that country in the seventeenth century, and refen-ing to statutes relating 

 to them even of the date 15SG. 



There were formerly three modes in •which paperhangings were manu- 

 factured. By printing the outline with blocks and then colouring by liand; 

 by stenciling ; and by blocks alone. 



The first of these methods is that described in my former paper, under 

 the head of Dominoterie. 



Thi' second, stenciling, is performed by cutting out either in paper, 

 leather, or othi>r materials, the pattern intended to be represented, and 

 then, placing this on the prepared ground, bnishing it over with the proper 

 colour. This mode gives an imperfect outline, and is now disctmtiiuied in 

 paperstaining, and merely sometimes employed by plasterers to ornament 

 coloured walls. 



The third is the mode now almost universally adopted in tliis manufac- 

 ture, whereby every coloiu- is applied by a separate block, according to the 

 tints and shadows hitended to he represented. 



I have before said that Lanyer's patent did not even mention paper 

 among the stibstanccs on which flock could be applied, as it was at that 

 period of loo rotten and bad a quality to bear the weight of the woollen 

 material. But paper has now been brought to so high a degree of perfection 

 that it is the only substance employed, and has thus assisted greatly the 

 operations of the paperstaiaer. Till within the last twelve years the pieces 



of paperhangings were formed of sheets, each about three quarters of a 

 yard long, pasted together till the proper length of twelve yards was com- 

 pleted. This method was attended with many ineonvenienecs, the joints 

 rising, or being imperfect, and generally showing, all which evils are now 

 remedied by the pieces consisting of one perfect length of paper, without 

 any joints whatever; tlie width, too, can be enlarged to two or three times 

 the ordinary size, as is now repeatedly done in France, as these examples 

 will show, though we have not as yet adopted this plan. 



The modern coloured papers are almost all worked in distemper, or 

 eoloiu- mixed with size to bind it, instead of with oil or varnish, which 

 was more employed formerly, and is now, in fact, used in the manufiic- 

 ture of the wasliable paperhangings ; the effect of Ihem, however, is not 

 nearly so clear and brilliant as in those ■\\orked by the former method. 



Distemper, or body colour, is generally thus prepared : — Whiting finely 

 powdered and soaked in water is first well mixed, as stiffly as it can be 

 worked, ami then stained with the proper colours well ground in water ; 

 when the desireil lint is produced, double size melted, with about an equal 

 proportion of water is added, till the colour is about the consistency of 

 cream, and when chilled it is fit for use. 



Commencing with the more simple papers, the first process is that of 

 laying the grounds ; to do this, the paper being placed on a bench about 

 twelve feet long, the workman with two large brushes filled with colour, 

 one in each Iiaud, passes them o\'er the paper with a circular motion, antl 

 as each piece is completed it is supported and carried by the attending boy 

 on a stick, and placed on the rack to dry. 



An ingenious machine has lately been invented, in which by three brushes 

 acting, one Avitli the other, the grounds are completely and evenly coloured, 

 and in a much more expeditious manner than by hand. 



The grounds being prepared, we will proceed with the printing, which is 

 performed by means of blocks. They are carved most generally in pear 

 tree, mounted on white deal ; the design being first traced on the wood, 

 the engraver or cutter, takiag care to follow the exact oittlinc, cuts perpen- 

 dicularly to the depth of one-eighth of an inch, and then slopes off till he 

 gets to the deal. I should add that where veiy sharp lines or dots are re- 

 quired metal is inserted in the block. 



The colour with which the printing is to be performed, being mixed to 

 the proper tint, is spread with a bnish on what is called the sieve — a 

 wooden frame covered with a blanket — the block is pressed on this and 

 then applied to the paper, on which it leaves the impression of the design. 

 There is a method of printing by a patent machine, invented by Messrs. 

 Archer and Taverner, whereby, by placing the blocks on the sieve and then 

 on the paper is performed with great exactness, with the labour of merely 

 turning a lever handle, which is done by a boy. It was foiuid, however, 

 too cumbrous to move. 



In the first case the pattern is given to the paper by a single block, but 

 as in the second, where there are two shades of colour, two blocks are 

 necessary. Now in order that the second block may be placed exactly in 

 its proper situation, you perceive that there are pin marks in each block 

 corresponding with each other, and on the marks printed by the first block 

 the pins of the second block are placed, and the pattern is thus completed 

 with the required correctness. 



In another ease a veiy delicate and shaded effect is given by a single 

 impression, wlrich is produced by what is called pin-work on a cyluuler. 



The pattern is formed by small brass pins of various sizes, fixed on a wooden 

 cylinder at difierent spaces, according to the depth of shade required. This, 

 fixed m a machine, is made to revolve so as to be supplied with colour from 

 a blanket, and at the same time print the piece of paper very speedily 

 without any interruption. This process, only lately applied to paperstaining, 

 is derived irom one much resembling it, in use in calico printing, only that 

 the latter so far differs that the colour is contained inside the cylinder, and 

 the pattern represented by holes pierced in it instead of pins fixed on it. 



In other cases the pattern is worked on what is called a blended gromid ; > 

 this is also a modern invention, originating, I believe, in France. The 

 blending is performed by a maehine piuposely constnicted. A metal 

 trough, the length of the breadth of paper, containing about twenty divi- 

 sions, has in those divisions various tints of colour, according to the blend- 

 ing required ; a long narrow brush is then dipped into the trough, and 

 being filled with colour, applies it to a roller, from which it is collected by 

 a large cylindrical brush the same length, which is made to revolve, and 

 when it is properly supplied witli colour it is then brought to bear tipon 

 the paper, on which it thus places the grounds, though in order to make it 

 suliiciently perfect it is necessary to be done twice. 



A common marble paper is printed by blocks in the ordmai-y way, and 

 afterwards varnished with turpentine varnish, by wlrich process it is enabled 

 to bear wasliing, water not injtiring it. 



There is an improved imitation marble paper, made by Arclier and 

 Taverner, in whicli, if assisted by a few veins laid in by hand, the effect is 

 certainly much superior to the last. The operation is considered secret, 

 but it is casv to be perceived that the mode of makmg it nearly resembles 

 that emploved by the makers of the bookbinders' marble paper in which 

 thickly guinmed colours are made to float on the surface of water, and 

 being stirred in various forms, are tlms absorbed by the paper when applied 

 to them. 



In an imitation of wainscot the ground is combed as in the usual 

 painted imitations of tliis wood, and the veins are afterwards printed. 



The satin ground paper is a great improvement on the common grounds, 

 and enables the manufacturer to produce imitations of silks and satins, which 

 luivo a lery elegant appearance. I have made every exertion to discover 



