STATE GEOLOGIST. 163 
stream of water about 6 inches wide under as great a pressure as possible. 
In one case known to the writer the water is under a pressure correspond- 
ing to a 70 foot water column. ‘The effect upon the molecular structure 
of a slag by granulating it by means of water has already been discussed. 
Practically themettecmus: extremely marked. Ay i rench engineer, El: 
Detienne, has approached the point from the practical standpoint, by 
grinding granulated and ungranulated slag together with equal amounts 
of hydrated lime. The cements thus produced were made up with stand- 
ard sand in the proportion of I part of cement to 3 parts of sand, and 
tested for tensile strength. After 28 days the ungranulated mixture 
showed a tensile strength of 60.2 pounds per square inch, while the gran- 
ulated slag mortar indicated 126 pounds. ‘Tetmayer found much great- 
er differences owing probably to the fact that Detienne used samples of 
slag cooled rapidly in the air and also did not grind his cement very fine. 
The water used in granulation probably does not enter into combina- 
tion with the slag to any extent, and the only change is the removal of 
part of the sulphur of the slag, going off as hydrogen and calcium sul- 
phides. Granulation of the semi-solidified slag has but little effect on 
its hydraulic value. 
Drying.—The granulated slag, after its excess of water has been 
allowed to drain off, is conveyed to the dryer; a rotary dryer 30 feet long 
and 5 feet in diameter, fired either with gas, crude oil, or coal is the most 
satisfactory. It has often been asked how slags too high in sulphur 
might be improved by the complete or partial elimination of this injurious 
ingredient, and it has been proposed to carry on this refining 
process during the drying operation. But as yet no definite or satisfac- 
tory scheme has been worked out. The use of steam and carbon dioxide 
has been suggested and some work has been done along this line. It 
seems that the use of steam offers a promising process, since it has been 
shown that the calcium sulphide is to a large extent decomposed by it. Hf, 
however, saturated steam is to be used, it is evident that this treatment 
must precede the drying owing to the condensation of steam. If, on the 
other hand, superheated steam is used, which also is the more efficient, 
the two processes could be combined. The dryer would have to be made 
much longer in this case, as long as a rotary kiln, 60 feet. By introduc- 
ing the steam at a distance of, say, 20 feet from the discharge end of the 
apparatus and the hot gases from the coal fire, gas jet, or oil burner at 
the lower end as usual, condensation at the discharge end would be 
avoided entirely. The temperature of the steam should not fall below 
300° C. In this connection it might be stated that the sulphur present as 
calcium sulphate evidently can not be expelled by this procedure. By 
maintaining reducing conditions of the fire gases, the expulsion of sulphur 
should be assisted most decidedly, especially if the temperature ap- 
