On Mortars, Water Lime, Cements, ^c, 113 



*' In order to afcertain perfedlly the tenacity of this cement, I caufed moulds to be made 

 fix inches in length, fix in width, and four in thicknefs, forming fmall mafles of 144 cubic 



inches. 



" Compofition of the cement, 180 cubic inches of bafaltes, 73 of lime flaked (fufee a la 

 romaine) 93 inches of fpring water, and a88 ftones of granite of the fize of a nut, the 

 whole forming a cube of 534 inches. 



*< Two moulds of a 144 inches each were filled with this compofition. One of thefc 

 was immerfed in the fea for 76 days, the other remained in the air for the fame time. 



" When the tenacity of this raafonry was to be tried, the extremities of thefe mafles 

 were placed on the edge of a piece of iron : each of them was loaded with a kind of wooden 

 trough, very narrow at bottom, placed acrofs the middle of the mafs, and gradually loaded 

 with balls of lead. 



*' The fame operation was formed with two fimilar bricks of Italian Pouzzolana, having 

 the fame proportions, and having remained likewife 76 days in the fea. It fupportcd 123 

 pounds before it broke, whereas the piece which remained 76 days in the air, broke under 

 a charge of 7 1 pounds." 



All thefe proportions, as the writer obfcrves, are infinitely too fmall to eftablifh an exaft 

 ratio, but it may neverthelefs be concluded, that the Pouzzolana bafaltes of Burgundy is 

 nearly as good as -that of Italy, which comes to us by Toulon. 



Citizen Ceflart in the fame letter, demanded fix thoufand weight of this Pouzzolana to 

 repeat his experiments on a larger fcale ; to which it appeared, that the difficulties and ex- 

 pence of tranfportation were at that time an obftacle. But this would no longer be any 

 impediment ; as the canal of the Saonc and the Loire Is in full navigation, and the extin- 

 guiflied volcano of Drevin is no more than one myriameter diftant from it. 



Another material ftill more common than bafaltes, and which may fometimes be a fub- 

 fVitute for pouzzolana, is the aflies of pit coal, provided it be a heavy cakeing coal, leaving 

 behind it rather a fcoria than a cinder. 



I likewife fent this article to Cherbourg in 1787, under the name of light pouzzolana, 

 to diftinguifli it from that which was made with bafaltes. It was fubmitted to the fame 

 comparative experiments, and afforded the following comparative refults, as is ftated in the 

 letter of Citizen Ceffart. 



" The bricks which had remained 76 days in the air, fupported charges of 115 and 137 

 pounds before they broke. 



" The fame blocks immerfed in the fea likewife for 76 days, broke with 48 and 30 

 pounds, confequently they had loft their confidence in the water of the fea." 



We obferve, that mortar made with this aflies is evidently fuperlor to that formed with 

 "the pouzzolana of Italy, as its tenacity is almoft double. It cannot indeed be employed 

 under water like the cement of water lime, but it is probable that it would fucceed very 

 well in works which are conftrudled dry, and are not to receive water until they have ac- 

 quired folidity. 



Vol. v.— June 1801. Q^ With 



