74 



or artificial stones that have just been described. It also, 

 nowever, is only an unburnt earth, not tempered, but 

 slightly moistened ; rendered very fine, then squeezed and 

 well beaten in large or small moulds, or between two 

 boards strongly fastened to each other, by which means 

 can be constructed. inclosures, walls and houses of several 

 stories of no greater thickness than is common in masonry. 

 " It would appear almost incredible," says Mr. Rosier, 

 " if experience did not support the assertion, that walls of 

 earth could last many centuries, provided they are well 

 plastered with mortar, protected from the rain, and secured 

 against moisture by foundations in masonry raised above 

 the level of the earth." 



As to the kinds of earth, there are very few which are 

 not suitable for pise, except pure clay, because it cracks 

 in drying, and pure sand, because it admits of no adhe- 

 sion. Where there is a choice, the preference is to be 

 given to that which is stiff that which sets or clods 

 easiest ; which is known by its retaining the shape given 

 to it by the hand, without sticking to the fingers such 

 generally is the untried earth of gardens. Stiff earth, 

 mixed with gravel, provided it is not too coarse, is employed 

 with equal success ; it ought also to contain no admixture 

 of roots or manures, which by rotting would allow the air 

 to penetrate and injure the wall. As to the moistr/e that 

 this earth ought to have, it ought to be the same that it 

 usually has in a natural state, at two or three feet below 

 the surface. When it is well pulverized, it is put into 

 the moulds or between two boards, and well rammed or 

 beaten with rammers, which will reduce its volume and 

 allow more earth to be added, which must be beaten in 

 the same manner, until the moulds or boards are exactly 

 filled. 



Previously to adding more earth, the iat>t layer ought 



