kkl.] PENNSYLVANIA. 291 
)inmencement of Portland -cement manufacture in Pennsylvania, dry 
rocesses had not been looked upon with favor. The European plants 
len in existence used wet processes exclusively, differing only in the 
no lint of water that was used. 
A dry process can not well be used in stationary kilns, whether of 
)ine or chamber type, for even if the mixing be done dry it will be 
^cessary to add water in making the mixture into bricks. The nat- 
ral result was that these early plants used water very liberally — 
most as freely as the Michigan marl plants of to-day, and with far 
ore excuse for doing so. 
With the introduction of the rotary kiln a dry process became not 
ily possible but advisable, and the Lehigh practice of to-day is the 
suit. The usual Lehigh practice may be summed up as follows: 
The cement rock is crushed and dried, the first of these operations 
[ten taking place in the quarry. Large gyratory crushers are corn- 
only used for this work, while the drying is usually done in rotary 
L'iers. The necessary amount of limestone, also previously crushed 
id dried, is added, and the two materials are mixed and further 
;duced together. Occasionally a smaller gyratory crusher, breaking 
say one-half inch, is the next step in the process of reduction, 
ommonly, however, the mixture goes to ball mills, comminuters or 
Williams mills, and then to tube mills. Some of the plants use Griffin 
ills in place of those noted, while the Atlas plant uses the Hunt- 
gdon mill. 
The raw mixture is ground to a fineness usually not exceeding 85 
er cent through a 100-mesh sieve, and often falling much lower, 
ompared with the practice at plants using limestone-clay mixtures, 
lis is coarse work. It is less harmful than might be expected, how- 
ler, owing to the fact that most of the mixture is made up of cement 
)ck which is alread}^ naturally well mixed. 
The mixture is usuallv dampened (to prevent too much of it being 
lown out of the kiln) and fed to rotary kilns. Except at the new 
clison plant at Stewartsville, these kilns are commonly 6 feet in 
iameter and 60 to 110 feet in length. 
CHARACTER AND COMPOSITION OP THE PRODUCT. 
The analyses given in the following table will serve to show the 
imposition of the product of the Lehigh district. Of the 10 analyses 
uoted, those numbered 1 to 8, inclusive, are fairly representative 
sments. Analyses 9 and 10, on the other hand, are of a brand carry - 
lg a very low content of alumina and iron oxide and a correspondingly 
igh percentage of silica. 
