lit' On Mortars, Water Limey Cements, ^el 



Concerning JSeton, or Water Cement. 



Every compofition of mortar intended to hold under water, and capable of becoming 

 almoft inftantly folid, is called in French Beton. 



This water cement may be made in feveral manners: i. the mortar Loriot, if well made, 

 holds very well under water. I have ufed it in the walls of a terrace through which there 

 was not the fmallefl: filtration. I have a mafs of this mortar hollowed out into a bafon, 

 which when filled with water, and placed on a fheet of paper, does not fhow the flighted 

 trace of moifture. 



The mortar Lafaye hardens lefs fpeedily, but when once it has become folid, It holds 

 water very well witliout being foftened. 



3. The mortar fpoken of by Smeaton, compofed of equal parts of lime and trafs, or the 

 volcanic afties of the Hollanders, is a true water cement, as it does not yield at all to that 

 fluid. 



4. The compofitions of mortar with Pouzzolana may alfo be ufed under water, and 

 when once indurated, they furpafs all others for the hardnefs and refiftance to the motions 

 of the waters. 



The moft common water cement is made with the poor lime ftone, or water lime. It 

 IS formed into prifms in hard pafte, which are let down into the water, and form a wall, 

 or otherwife this material is poured between two walls, at the diftance of 2 1 or 22 metres 

 afunder, in the manner of coffer work, for the purpofe of forming a fuitable defence or 

 inclofure for waters in parts of canals above the furface of the ground. 



Methods of/upplying the Want of Pouzzolana. 



Pouzzolana is a volcanic fand which is brought from the environs of Naples. Though 

 the fuperiority of mortar formed with this material is well known and determined, yet it is 

 often neceflarlly difpenfed with on account of the expence of carriage, which fo greatly 

 enhances the price. 



But as we are well acquainted at prefent with a number of extinft volcanos in France, 

 we may find an abundance of materials to fupply the place of the Pouzzolana. The expe- 

 riment was made in 1787 by Citizen De CeiTart, engineer, charged with the conftruftion 

 of the cones of Cherbourg. In the month of Auguft of that year I fent him about 13 

 kilograms of the extinft vdcano of Drevin in the department of Saone-et-Loire. 



The bafaltes was firft heated in a fmall reverberatory furnace, then thrown red-hot into 

 water, and ftamped and fifted, fo that the largeft grain did not exceed the fize of a pea. 

 The following arc the refiilts of experiments on mafonry conftrufted with this cement of 

 bafaltes, compared with another cement from the Italian Pouzzolana, according to the 

 letter of Citizen Ceflart, dated Feb. i2j 1788. 



" In 



