CARPENTRY. 



541 





two sides BC, CA, will be fixed ; and because BCD 

 .ni^le, .mil the points B and C arc fixed ; the 

 1 ), ami eonstrquently the sides CD and DB are 

 ! : in like manner, since CDE is a triangle, and 

 points C ami D lixed, tin- point E will also be- fix- 

 , ;,iul also tin- snies DE and EC. The same 

 miy be shown in like manner for the points F and 

 G. Suppose, then, two equal and opposite forces 

 applied at the points A and G in the plane of the 

 ''lire can neither be extended out nor 

 compressed together. The pieces AH, HB, and 

 Gl, i F, are ot no other use than to make the centre 

 stand firmly on its base. This disposition of the tim- 

 bers will cause them to occupy the least possible space. 

 If the timbers are fixed at the points k, I, m. , o,p, 

 Fig. 1 1, the same immutability of figure may be de- 

 monstrated; for suppose the points A and H to be 

 fixed, the point K will also be fixed ; the points A 

 and k being fixed, the point B of the triangle A k B 

 will likewise be fixed ; again, the points B and k be- 

 lixcd, th_- point / will also be fixed : in the same 

 in.umer all the remaining points, C, m, D, n t E, o, 

 F, />, G, I, may be proved to be stationary in respect 

 of the points A, H; and the whole figure being kept 

 in i quilibrio by any three forces acting in the plane 

 of the figure at any three angles, the action of the 

 forces will only tend to compress or extend the tim- 

 bers in the direction of their length. 



In the construction of this truss, the triangular 



\- 

 CXXIX 



parts may be constructed all in the same plane, 

 and the pieces BD and DF may be halved upon 

 the pieces CA and EG ; but the utmost care mut 

 be :aken to secure the several pieces concurring at 

 each of the angles, by bolting or iron straps, as no 

 dependence can be put in any such joint without iron: 

 but perhaps the best method of any is to halve the 

 thickness of the pieces AC, CE, LG, at the points 

 C and E, and also the pieces AB, BC, CD, i 

 EF, FG, at the points B, D, F : then bolting tl...- 

 ends A and C of the pieces BA, BC, the end C and 

 E of the pieces DC and DE, and the ends> E and G 

 of the pieces FE and FG, and then fixing double 

 braces BD, DF, that is, fixing BD upon one side of 

 the truss, and another upon the other side of the 

 truss opposite to it, also fixing DF upon one' side, 

 and another opposite to it. 



Fig. 12. represents the manner of constructing a Fig. 12. 

 centre according to the principles of Perronet, the ce- 

 lebrated French ergineer, but the disposition of the 

 timbers, forming only a series of quadrilaterals, gives 

 nothing but immutability of figure. It can, there- 

 fore, only derive its stiffness from the resistance of 

 the joints. 



Having thus given a general account of the prin- 

 ciples of Centering as connected with the article 

 Carpentry, we must refer our readers to the article 

 BRIDGE for its application, and other practical re- 

 marks in the construction. 



CAR 



CARPESIUM, a genus of plants of the class 

 Syngenesia, and order Polygamia Superflua. See 

 BOTANV, p. 297- 



CARPET, in the manufacture of cloth, is a species 

 of woollen stuff, made of variegated colours, and used 

 for the fluor cloths of rooms. 



The manufacture of carpets, we may reasonably 

 conclude, originated in Aiia, from whence most of 

 our knowledge of the manufacture of cloths of al- 

 most every description appears to have been derived ; 

 and to this day, the finest and most expensive of the 

 ornamental kinds are distinguished by the name of 

 Turkey carpets. They are now, and hu.ve long been, 

 manufactured both in France and Italy, and those 

 used in Britain, of internal manufacture, are equal 

 both in fabric and design to any imported. In Eng- 

 land they are generally called Wilton carpets, from 

 the county which is the chief seat of that and the 

 other finer branches of the woollen manufacture. 

 Some manufactures are, and have been long establish- 

 ed in Scotland, of which Stirling and Kilmarnock 

 are the chief seats, but they are generally confined to 

 the coarser and low priced kinds. 



Carpeting possesses this peculiar property, differ- 

 ing from almost every other kind of cloth, that it 

 consists of two distinct webs, woven at the same time, 

 and firmly joined together by the operation. Hence 

 arises that common effect, that on the two sides oi a 

 .t the form of the pattern is the same, but all 



CAR 



the colours are reversed. The most accurate idea that 

 can be formed of the texture of carpets, is to suppose 

 the warps of two distinct webs to be placed in the 

 same loom, and in contact with each other, the one 

 being above and the other below ; and that the 

 weaver, in forming cloth, is to intersect each web 

 with one thread of woof alternately. Were this pro- 

 cess followed strictly, as in weaving plain cloth, two 

 separate webs would be produced, and the operation 

 would, of course, be much more clumsy and tedious 

 than the common mode. Again, if we suppose that 

 a carpet woven of double cloth were formed of lineal 

 stripes by the warp, two distinct fabrics of cloth would 

 be produced ; but these would be intersected and joined 

 by parallel straight lines, extending from one end of 

 the web to the other, at distances equal to the breadth 

 of the respective stripes. If further, we suppose 

 these stripes to be reversed at pleasure, and that this 

 should be so effected as to form the wholei nto a suc- 

 cession of squares, the appearance of a tesselated 

 pavement, or what architects and builders denominate 

 Mosaic work, would be the result. In this the junc- 

 tion of the two fabrics would be more intimate than 

 in the first, and the greater the variety of pattern, 

 where the figures are small, the intimacy is still in- 

 creased, because the webs are joined at a much greater 

 number of points. From this a very useful deduc- 

 tion may be gathered by those who study durability 

 more than ornament in the purchase of a carpet, al- 



Cmrpef. 



