CONSTRUCTION OF RETORTS. 93 



of the oven form, seven feet nine inches long, five feet wide and sixteen feet deep, capable 

 of holding and carbonizing 130 Ibs. of coal every hour, or seven cwt. in six hours. At 

 the end of the first week the deposit appeared about an inch in thickness, and when once 

 formed it accumulated more rapidly till the whole inner surface within a foot of the mouth 

 was covered with it : at the further end it rapidly filled up the retort, preserving an equal 

 thickness, until, at the expiration of two months, it had reached 24 inches in thickness, 

 stopping up the retort quite one-fourth of its length. Under the roof and upon the sides 

 of the remaining portion of the retorts, it formed a coating of not more than two or three 

 inches thick ; in four months more it would have filled up the whole. 



" We then had the substance cut through into two parts, and taken out ; when, after 

 allowing for some of the scattered fragments, it weighed full ten cwt. 24 Ibs. 



"The coal carbonized during the time of this experiment was 67 tons of Woodside 

 Wall's-end, the same having been used in nearly all the former trials ; the deposit, there- 

 fore, was in weight about l T 2 <jths per cent, of the coal carbonized, and undoubtedly occa- 

 sioned by the compression of the gas in the retort immediately after its formation. 



" I have applied myself to the means of taking off the whole of the pressure, which I 

 effected, excepting only the resistance offered by the half-inch dip in the fluid of the hy- 

 draulic pipe. Under this change of operations, after the same retort was again worked 

 with the Wood-side coals without interruption for four months, I had the satisfaction of 

 observing that scarcely any deposit appeared at the expiration of that time. 



" If I mistake not, this will prove a welcome discovery to all Gas Companies, more 

 especially to those where the Newcastle coal is used. 5 '* 



PLATE VIII. 



SPINNEY'S BRICK RETORT. 



Fig. 1 . represents a front elevation of the brick retort and hydraulic valve 

 of Mr. Thomas Spinney, of the Cheltenham Gas-works. 



Fig. 2. is a transverse section through the furnace. 



Fig. 3. is a longitudinal section through the centre of the oven and flue. 



A is the retort or oven. The bottom and sides are formed of Newcastle 

 fire-tiles ; the crown of fire-bricks is composed of Stourbridge clay, mixed with 

 about 10 per cent, of sharp river-sand and pipe-clay, which addition prevents 

 the bricks from cracking and improves them in other respects. The interior 

 dimensions of the oven are three feet two inches wide, eight inches to the 

 springing-line of the arch, and from thence to the crown six inches. 



The fire-bricks just spoken of, which compose the crown of the oven, and 

 also the fire-tiles which form the bottom and sides, are made with a groove 



