No. 112.] 793 



Carbonic acid, 23.10 



Silica, 3.70 19.60 



99.70 99.85 



<* No. 68 is copper pyrites, containing iron, as it usually does. 

 This is sufliciently rich in copper to make it valuable if found in 

 any considerable quantity. The greater part of the copper of 

 commerce comes from this kind of ore. No. 86 is a carbonate of 

 copper, and will be very valuable if found in adequate quanti- 

 ties.'' 



The hyperstene rock, occupying a wide range through most 

 sections of the county, abruptly terminates in contact with the 

 Potsdam sandstone in the Au Sable valley. The latter forms 

 for several miles the walled banks of the Au Sable river, and is 

 extensively dilfused over that valley. Lying in a perfect strati- 

 fication, it may be excavated in vast slabs and blocks, and affords 

 an invaluable material for building. 



A vein of "water cement" in the town of Willsboro', of a 

 very superior quality, has been used for practical purposes for 

 many years, and is apparently of great extent. Other deposits of 

 this material occur in various parts of tlie county. A sample 

 from one upon the premises of Harris Page, of Chesterlield, was 

 examined by Professor Salisbury. Ilis anal3ses of specimens 

 from both deposits are presented in the following table : 



No. 51. Ko. ZO. 



Irom WUli?Uro'. II. Pa^jc, rhostcrficM. 



Silica, 14.36 57.37 



Alumina and iron. 7.93 10.36 



Carbonate of lime, 00.46 . 17.43 



Soda,. ..V 0.73 0.06 



Magnesia, 13.40 7.93 



Potassa, 0.60 0.10 



Sulpliuiic acid, 0.20 0.23 



Chlorine, . .' 0.14 trace. 



f Organic matter. 1.60 • 0.46 



-- fc , 



99.98 99.88 



