GEOLOGY. 39 



MORTAR. 



We have a few remarks, on making it. This is commonly 

 a mixture of sand and slacked lime. When sand cannot be 

 had, pulverised dry clay or brick-dust, will answer as well. 



To the sand and slacked lime, if iron dust, or manganese be 

 added, a cement may be made, which will harden under water. 

 With such a cement, cisterns may be made, tan vats, and cel- 

 lar walls, that will answer many useful purposes. 



Compact lime, is often used, as a manure, and our shell 

 lune, is the best for that purpose. Sometimes, the stone is 

 only pulverised, sometimes it is burnt. Many of our marbles 

 that are full of shells, are very beautifully variegated, with 

 spots of different forms and colors. Sand and emery, putty 

 and tin filings, with water, are employed in polishing this 

 limestone. As yet, we have discovered but few beds, of this 

 stone, which are used as marbles. Time and further research 

 may discover to us, other marbles, at no distant day, in our 

 limestone region. It is quite probable, that the best marbles 

 lie deeper in the earth, than we have, as yet, sought for 

 them. 



Southwest of Springfield, on the road to Dayton, is a lime- 

 stone of peculiar appearance. Its structure and aspect re- 

 semble, those in western New York, where gypsum and lime- 

 stone abound. That near Springfield deserves examination, 

 by some one, acquainted with those minerals of western New 

 York. It is quite possible, that the limestone near Spring- 

 field may answer a good purpose for backs of chimneys, and 

 ought to be tried, by exposure to great heat, and, by then 

 throwing it into water, while thus heated. That it is an ex- 

 cellent limestone, for producing mortar, we doubt not, and by 

 mixing with it a proper proportion of sand, it may produce a 

 cement that will harden under water. 



