486. Effects of Temperature on Masonry. Frost is the most
powerful destructive agent against which the engineer has to
guard in constructions oi masonry. During severe winters in the
northern, parts of our country, il lias been ascertained, by obser-
vation, that the frost will penetrate earth in contact with walls to
depths exceeding ten feet ; it therefore becomes a matter of the
first importance to use every practicable means to drain thoroiighly
all the ground in contact with masonry, to whatever depths the
foundations may be sunk below the surface ; for if this precau-
tion be not taken, accidents of the most serious nature may hap-
pen to the foundations from the action of the frost. If watei
collects in any quantity in the earth around the foundations, i



,dhy Google



CONSTRUCTION OP ilASONRV. IGl

may be nei;essary to make small covered diaiiis under them ta
convey it off, and to place a stratum of loose stone between tho
eidca of tlie foundations and the suiTounding earth to give it a
free downward passage.
