192 [Assembly 



carbonic acid gas which it lost in burning much more rapidly than the 

 hme made from compact, fine grained stone, and if used as soon as 

 mixed, makes better mortar than the hard stone lime, as was proved 

 by the late Lord Stanhope, of England. 



When mixing mortar, the fine angular silicious sand, free from ear- 

 thy substances should be used ; that obtained from the shores of riv- 

 ers is probably the best. If your sand contains much earth, the 

 mortar will be sensibly weakened. Sea-sand is not good for the reason 

 that it contains salt, which has the effect of attracting moisture, and 

 preventing the walls from becoming dry. The more labor you ex- 

 pend on the manufacture of a bed of mortar, in mixing and thoroughly 

 incorporating the particles of lime and sand, the better will be its 

 quality. Our mortar is very inferior to that which was made twenty 

 years ago even in this city, and the reason is that the same care is not 

 generally taken in the selection of materials, the labor and propor- 

 tions of lime and sand. It is not a rare thing to see a raw emigrant 

 from the Emerald Isle, mixing mortar in our streets without further 

 instruction than this from his employer : " There is a heap of sand, 

 there twenty barrels of lime, and here the pump ; I wish you to make 

 It into mortar." He who never saw lime before, makes the mortar, 

 and what is it but an inferior substance, incapable of binding either 

 brick or stone. The strongest water cement now known is made of 

 a substance called pozzuolana, which is found near a city named Poz- 

 zuoli, not far from Naples, in Italy. It consists of volcanic ashes, 

 concreted into a rusty mass, and when mixed with sand and lime it 

 sets quick, and becomes as hard as any stone under w^ater. There 

 are numerous moles and foundations for summer residences, built in 

 the bay of Baird, by the Romans, who made use of this substance. 



The Dutch have something similar, which they call trass, made 

 from porous lava found at Andernach, on the banks of the river Rhine, 

 in Germany. It is ground fine and mixed with mortar, and makes a 

 valuable cement for hydraulic purposes. 



Grout is mortar made liquid by an admixture of water and is pour- 

 ed over brick work when recently laid : it finds its way into all the 

 interstices, and cements the whole into a comparatively solid mass, 

 when great strength is desired this course should always be pursued. 



The Chinese probably knew the use of mortar long before the 

 Greeks and Romans, and consequently the use of the arch, in fact no 



