56 ANNUAL OF SCIENTIFIC DISCOVERY. 



by a wheel keyed upon the end of the shaft of the fixed roller and 

 three pair of bevel-wheels. The bevel-wheels are driven by a pinion 

 keyed upon the end of the main driving-shaft of the machine, which 

 shaft also gives motion, by means of an upright shaft and suitable 

 gearing, to the screw, which forces the clay contained in the cylinder 

 through the die. The rollers are thus driven in the same direction 

 and with the same surface velocity. The process of manufacturing 

 pipe according to this invention is therefore as follows. The clay, as 

 it is forced through the die in the form of a pipe, slips over the man- 

 dril. The length of pipe required is then cut off, and afterwards 

 drawn by the motion of the rollers over the end of the mandril, where- 

 by the particles of matter forming the pipe become compressed to 

 such an extent, that, when baked in the usual way, they have been 

 found, by repeated experiments, to be upwards of 75 per cent, stronger 

 than pipes made from the same clay, but manufactured in the ordinary 

 manner, besides being better finished in every respect. 



Instead of compressing the pipes immediately after passing through 

 the die, if the weather or the consistency of the clay render it desira- 

 ble, they may be allowed to stand for a day or two. In cases where 

 the pipe is to have a taper hole, a mandril is used made taper at the 

 point, the mandril being gradually withdrawn by a screw or other 

 suitable means, during the time the pipe is passing between the 

 rollers. When the article to be compressed is not of a circular form, 

 the number and position of the rollers are so changed as to leave the 

 aperture at the centre of any shape required, instead of circular, as 

 above described. In this way oval pipes, stair steps, &c., are formed, 

 and by having the rollers engraved with a device it will be impressed 

 upon the article. The hollow bricks or tiles are formed by forcing 

 clay through a die of suitable form, and afterwards compressing the 

 clay, by passing it between four rollers, two of which are turned of 

 such a form as to produce a rebate on the edges of the bricks ; the 

 other two being engraved on their peripheries, so as to produce on 

 the sides of the brick or tile any desired device. The ends of the 

 brick are rebated afterwards in a separate machine. Another part of 

 these improvements relates to the mode of making bends for pipes, 

 and consists in so constructing the die that a bend of any required 

 curve can be produced, simply by forcing the clay through it, where- 

 by the moulds heretofore used in making bends are dispensed with. 

 Civil Engineer and Architect's Journal, Jan. 



IMPROVEMENTS IN FIXED AND REVOLVING LIGHTS. 



THE London Civil Engineer and Architect's Journal contains a de- 

 scription of a " new dia-catoptric instrument for increasing the in- 

 tensity of the light in revolving or fixed lights." The instrument 

 consists of three parts, a paraboloidal mirror, having the conoidal 

 portion behind the perimeter cut off, and its place supplied by a hem- 

 ispherical reflector, whose centre thus coincides with the focus of the 

 paraboloid, while in front of the flame is placed an annular lens, sub- 

 tending, at the focus of the paraboloid, the same angle as that which 



