STATE GEOLOGIST. 309) 
tacle. The clinker drops down the grate while air enters at the inlet 
(sce figure 55). The heated air is exhausted by means of a fan, with 
water jacketed bearings. This apparatus was patented by Galschioet and 
seems to be a compact machine which does not occupy as much space as 
the inclined cylinder cooler and can be fed direct from the kiln, requiring 
no elevator. The clinker is removed by a screw conveyor. 
It would be idle to attempt to save the heat from the clinker in a 
dry mixture plant while no attempt is made to get back some of the much 
greater amount of heat lost from the short kilns. What is needed most 
urgently at present is the close regulation of the air inlet into the ordinary 
kiln. That this can be done is affirmed by Mr. H. E. Brown, chemist of 
the Coldwater, Mich., Portland Cement Works, who stated to the writer 
that the analysis of the gases in his kilns showed an air admission of 97 
per cent., using the wet method. It is necessary that strict control be 
kept of the firing conditions in our kilns by means of the Orsat or 
similar apparatus. 
The Edison kiln 150 feet in length solves the entire problem of 
fuel consumption by allowing combustion to take place some distance from 
the lower end. ‘The air is thus naturally preheated by the clinker and 
heat radiated from the zone of combustion while the waste gases are 
cooled down sufficiently by the long tube and are made to preheat the 
mixture. 
REFRACTORY KILN LINING. 
The question of the kiln lining is an important and much disputed 
one. In the majority of cases high grade fire brick are used in the 
combustion zone and lower grade brick in the cooler portions of the 
kiln. The whole question of refractoriness hinges, first, on the chemical 
composition of the material, and, secondly, on its physical characteristics, 
size of grain and porosity. Since the lining is in contact with a basic 
material, we would hardly expect that a silicious lining would prove satis- 
factory, although the sugar industry has used for lining its limekilns 
quartzitic rocks with fair success. It is generally assumed that the clay 
substance in its ideal compositon is the best possible refractory, but we 
are at once confronted by the question of the kind of clay substance. 
We know in nature three distinct kinds of clay substances; the kaolin, 
forming a somewhat friable, slightly plastic mass which burns to a 
porous body; the horn-like, plastic ball-clay having almost the same 
composition, but containing small quantities of fluxes. This becomes 
dense even when burnt at low temperatures,, but still has a high melt- 
ing point; and lastly, hard non-plastic, flint clay. The kaolin is much 
more infusible than the ball-clay, showing a difference of perhaps 3 or 4 
cones in actual melting point, but after all it does not stand up so 
well in the fire in contact with fluxing materials, slags or glass, simply 
because it is too porous in structure, allowing fused bodies to enter 
