35 A STATISTICAL ACCOUNT OF THE 



into the composition whereof, salt hair does not enter. 

 Chemists may account for this: but to them it is not yet 

 clearly ascertained, from whence the muriatic acid is de- 

 rived; nor are its nature, and properties, accurately 

 kno\vn. Long and frequent experience has evinced, 

 that the least mixture of this acid, or common salt,^ 

 with gypsum^ produces a tertium, which renders it unfit 

 for a cement; and also destroys its agricultural uses and 

 properties. 



RECIPE FOR COMPOSITION TO IMITATE 



STONE. 



The w^ork should not be primed; though part of that 

 at the bridge was so done, before it was determined to 

 coat it with composition. 



The paint used was common white lead and oil ; as 

 the painters preferred their own way, and the scaffolding 

 could not remain at risque, while experiments on other 

 paints were tried. It was conceded afterwards, that if 

 there had been time to prepare and use other paint, and 

 the urgency of dispatch had not precluded delay for dry- 

 ing, Jish oil and clarijied turpentine with ochresy would 

 have been more eligible. 



* Common salt is compounded of the muriatic acid^ and 

 soda. The latter substance abounds in the ocean, and other 

 places, where co7nmon salt is found. The vitriolic acid oi gyp- 

 sum meeting with the muriatic^ in the salt^ expels it from the 

 soda of the salt ; and having a predominant affinit}^, forms suU 

 phat of soda^ or glauber salts. Good common salt should 

 contain two thirds of soda^ and one third of muriatic acid ; 

 and is seldom pure in its combination, as to proportion .; oi- 

 ;<bsence of foreign matter. ^ 



