30 



Mineralogy of Neio York. 



Carbonic acid, 



Lime, 



Magnesia, 



Silica 



Alumina, . 



Peroxyd of iron, 



Loss, 



and remarks that the calcined product approaches in composition 

 a double silicate and aluminate of lime and magnesia. The fol- 

 lowing are his analyses of other hydraulic limestones. 



Prof. B. remarks, that "the process of burning or calcining the 

 limestone requires great care. A limestone, very proper in other 

 respects, gives, when the heat is urged too high, what is called 

 a dead lime, in consequence of the partial fusion of the mass ; 

 whereas, when the calcination is effected at too low a tempera- 

 ture, the resulting lime is meagre, and not hydraulic. 



" Hydraulic lime should be used as soon as possible after cal- 

 cination ; and when kept for any time, it should be carefully 

 protected from the action of the air. It has been ascertained that 

 the hydraulic property of limes is much weakened by their being 

 exposed to the air ; and consequently, all other things being 

 equal, recently prepared hydraulic lime is to be preferred for im- 

 portant structures, to that which has been for some time manu- 

 factured. 



" It is generally agreed that the rapidity with which hydraulic 

 mortar hardens, and the ultimate degree of hardness which it 

 acquires, depend greatly upon the proper proportions of lime and 

 sand, their intimate incorporation, and the amount of water em- 

 ployed in their mixture. All these are points which must be 

 settled by previous experiments." — p. 77. 



In Ulster County, where the hydraulic limestone abounds and 

 is largely worked, the following is the mode of preparation. 



