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balls passed easily through the walls of pise", but did not 

 shake them, while it upset easily and with a great crash 

 those walls in round or hewn stone. At any rate, if, as 

 it has been said in the beginning, it is desired, like Coin- 

 tereau, to make pise" beforehand under sheds, in small 

 moulds, as well for greater facility as to secure greater 

 hardness and a more equal compression, and to avoid the 

 irregularities of the seasons, etc., this is what we have 

 first to consider. Experience has generally proved that 

 fine earth, being pressed to half its volume, as is neces- 

 sary for greater solidity, weighs always from 120 to 160 

 Ibs. the cubic foot, according to the nature of the ele- 

 ments which it contains ; now a cubic foot contains 1,728 

 cubic inches thus, an artificial stone or brick of pise", 

 the fourth of a cubic foot, will weigh 30 to 40 Ibs., which 

 would still be a great deal to be handled easily by one 

 person, as it would often be necessary. Besides, experi- 

 ence has equally proved, that a person could do more 

 work with small hewn stones, than with too large, in a 

 given time ; wherefore it would be well to reduce ours to 

 the fifth or even the sixth of a cubic foot ; they will still 

 weigh 20 to 25 Ibs. Now, if we are satisfied with a wall 

 eighteen inches thick, which is suitable for many circum- 

 stances, we can content ourselves with artificial stones of 

 six inches wide, four inches thick, and twelve inches 

 long, making 288 cubic inches, or one-sixth of a cubic 

 foot ; in short, one of these stones lengthwise, and another 

 across, and so on alternately in the construction of the 

 wall, would enable us to keep exactly and always this 

 thickness of eighteen inches ; and if we wished to extend 

 this thickness to two feet or reduce it to one, as partition 

 walls would probably require, nothing would be easier, 

 since in the first place it would be enough to put two slones 

 end to end, and in the second, it would only be necessary 



