100 THE SCIENTIFIC PAPERS OF 



cellent qualities, but, that it was not the only one possessing im- 

 portant improvements. The plan had been tried, indeed, at 

 Lambeth, with this difference, that coal was burnt to effect the 

 carbonization, the gases being used for illuminating purposes. 

 Those ovens were being pulled down, because the gas produced in 

 them was found to be deficient in brilliancy. Those most in use 

 on the Continent were of two different descriptions. The first, was 

 a semi- cylindrical horizontal oven, closed at the ends with 

 movable doors, and provided with a covering arch forming an 

 annular chamber, through which the gases generated in the oven 

 circulated, and were consumed there by the admission of atmo- 

 spheric air, in order to continue the distillation of the coal inside. 

 That was an improvement, inasmuch as the gases did not go 

 to waste ; and he believed ovens of that description were used at 

 the Ebbw Yale works, with great effect. In South "Wales excellent 

 coke was formed by mixing anthracite with bituminous substances, 

 and by exposing the mixture to great heat in close ovens. 



Another description of coke-oven which he had seen in France, 

 and which seemed to be a favourite in many establishments, was 

 in the form of a number of upright retorts, and was known as the 

 " Four Appold." Each retort was slightly conical, and was filled 

 by shooting the coal from carts at the top. The gases evolved, 

 passed through the sides of the retort, and were burnt there by 

 the admission of atmospheric air. After a distillation of 24 hours 

 or 40 hours, a trap-door at the bottom was opened, and the whole 

 of the coke, amounting to several tons, was dropped into railway 

 trucks, or carts, and carried away. That was another instance 

 where the full value of the carbonaceous material was obtained. 

 He might mention, also, an oven he had lately tried, which was 

 based upon the same principle, as regarded the general arrangement. 

 It was an upright retort, but, instead of being simply heated by 

 the gas issuing from the coal, a poorer kind of gas was used, which 

 had been previously heated by passing through a regenerator ; the 

 air necessary to combustion being also passed through a regenerator 

 placed at the side of the retorts, so that only a portion of the gases 

 evolved was required to heat the coal, the rest being applied to 

 other uses, either for illuminating purposes or for the heating of 

 working furnaces, &c. He had noticed the remarkable fact, 

 that when the gas was drawn from the bottom of the retort, 



