194] HYDRAULIC LIMESTONE. 55 



HYDRAULIC LIMESTONE FROM EASTPORT. 



Insoluble Matter 35.281 



Potash 0.348 



Lime 32.603 



Magnesia 0.630 



Peroxide of Iron 1.581 



Alumina 1.914 



Carbonic Acid, Water, and Loss 27.643 



100.000 

 For want of a sufficient quantity of material, I have been una- 

 ble to make reliable experiments on the comparative rapidity of 

 "setting" of the cement burnt from this rock ; it seeing however, 

 to solidify somewhat less rapidly than that from Billing's mill. 



94. While these analyses, as well as the experiments made, leave 

 no doubt as to the adaptedness of these rocks to the manufacture 

 of excellent hydraulic cements, it must be recollected, that for 

 each variety of hydraulic limestone there exists a certain degree 

 of burning, after receiving which, it hardens best, or most rapidly. 

 If on the other hand, the burning exceeds, or falls short of, that 

 particular degree, the hydraulic properties will be the more im- 

 paired, the farther the burning given varies from the proper degree. 

 The latter can only be determined by experiments on the large 

 scale, in kilns properly constructed ; the general rule being, that 

 hydraulic limestones require much less burning, than those yielding 

 quicklime. On account of the inequality of temperature which, 

 always prevails in the common lime-kilns, where the process is in- 

 terrupted in order to draw the charge, these are altogether unsuit- 

 ed to the burning of hydraulic cement ; and since, moreover, the 

 manufacture of the latter involves, of necessity, the establishment 

 of a mill (for grinding the calcined rock), and therefore, pre-sup- 

 poses the existence of a constant demand to be supplied by contin- 

 uous manufacture, the "perpetual" kilns, in which the burning goes 

 on without interruption, are alone adapted to this purpose. 



In view of the lively demand for hydraulic cements which exists 

 in this State ; of the high tax imposed on the consumers of this 

 article by the long transportation which it has to undergo at pres- 

 ent, and of the convenient accessibility of these deposits by way of 

 the Tennessee River, while distant only 7 or 8 miles, at their 

 nearest points, from the M. & C. R. R. (to which access might also 

 be had, at high stages of water, on Big Bear Creek) there is rea- 



