CHAPTER IV. 
OF SAND. 
IN buildings of rubble work it is of the first importance 
that the sand be fit for mixing with the lime, and unal¬ 
loyed with earth. The different sorts are these; black, 
white, deep red, and bright red. The best of each of 
these sorts is that which, when rubbed between the 
fingers, yields a grating sound. That, also, which is 
earthy, and does not possess the roughness above named, 
is fit for the purpose, if it merely leave a stain or any par¬ 
ticles of earth on a white garment, which can easily be 
brushed away. If there be no sand-pits where it can be 
dug, river sand or sifted gravel must be used. Even sea 
sand may be had recourse to, but it dries very slowly ; and 
walls wherein it is used must not be much loaded, unless 
carried up in small portions at a time. It is not, however, 
fit for those walls that are to receive vaulting. In plas¬ 
tered walls, built with sea sand, the salt which exudes de¬ 
stroys the plaster; but plaster readily adheres to and 
dries on walls built with new pit sand, and vaulting may 
safely spring from them. If sand have been dug a long 
time, and exposed to the sun, the moon, and the rain, it 
loses its binding quality, and becomes earthy; neither 
when used does it bind the rubble stones together so 
as to prevent them sliding on their beds and falling out: 
nor is it fit to be used in walls where great weights 
are to be supported. Though pit sand is excellent for 
mortar, it is unfit for plastering; for being of a rich