COKE MANUFACTURE. ite 
Though the furnace.is somewhat expensive in its construction, it is said 
to have worked successfully, though with some coals the bottom part 
was not always well coked, as is also the case often with the other forms 
of ovens of this class. To obviate this, Mr. Parry, of Ebbw Vale, con- 
structed some furnaces on Cox’s plan, but the gases, instead of passing 
directly into the chimney, descended first and circulated underneath 
the hearth, through flues made in the bottom, which communicated with 
the chimney ; the furnace was therefore heated well on the bottom, and 
the coal uniformily coked. 
OVENS OF THE SECOND Crass. Im the ovens of the first class, 
as already described, the bed of coal exposed is always of considerable 
thickness, and the operation of coking is begun from the top, by the 
heat stored up in the vault of the oven from a previous operation, and 
proceeds downward to the bottom ‘of the oven. Unless the coal con- 
tains sufficient volatile matter to furnish the heat necessary, or the coal 
is of a strong coking character, the operation will be incomplete and 
the mass not thoroughly coked. From a too thick bed of coal or too 
little heat in the oven, a cold or damp bottom, the coking is often in- 
complete, leaving a stratum of uncharred coal on the bottom of the 
oven. ‘The ovens of this class are specially adapted for the very best 
or strongly coking coals, and when the dry or light coals are to be 
used, the ovens of the second class are better suited, where the prism of 
coke is thinner and the heat more uniformly applied to the coal, the 
walls being heated from the interior. In these the coking operation 
proceeds from the sides toward the center, and when very dry coals are 
used the prism of coal should be very thin. 
The ovens of this class are round and elliptical, as the Breckon and 
Dixon, etc., or as is more common, rectangular; placed vertically it is the 
Appolt oven; horizontal, it forms the large class of Belgian ovens. The 
ovens may only be heated on the bottom, as in the ovens of Panwell, 
Dubochet, Pernolt, etc., by fuel burnt separately beneath them, which 
is, however, applied only when the gas evolved is to be further 
utilized, or the bottom may be heated by the gases from the coal itself, 
as the Breckon and Dixon oven. More commonly they are heated by 
flues passing through the walls and under the bottom, in which the gases 
evolved from the coal burn and produce the necessary heat in the Bel- 
gian type of furnace, the Linet, Coppee, Fabry, Francois, Dulait ovens. 
The Breckon and Dixon oven, * patented in 1860 in England, con- 
