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 tnuriatic acid is de- 

 rived; nor are its nature, and properties, accurately 

 known. 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 work 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 scaifolding 

 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 ochres^ would 

 have been more eligible. 



* Common salt is compounded of the 7niiriatic acid^ and 

 .'ioda. The latter substance abounds in the ocean, and other 

 places, where common salt is found. The vitriolic acid oigijp- 

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

 soda of the salt ; and having a predominant affinity, forms 5i//- 

 phat of sodoj or glauber salts. Good common salt should 

 contain txvo thirds oi soda^ and 07ie third of muriatic acid; 

 and is seldom pure in its combination, as to proportion j or 

 absence of foreign matter. 



