For jointing drainpipes, cement mixed with a little sand is used. When the sand is clean and sharp, 1 part of sand to 4 parts of cement may be safely used, without detracting too much from the strength of the joint. To make a good joint, tarred gaskin should be first well caulked into the joint with aflat caulking tool, so as to prevent the cement mortar bulging up inside the pipe and forming a ridge. The length of time such a joint should be allowed to stand before testing will depend on the setting qualities of the cement, but with twenty-four hours' rest it should stand a head of 1ft. of water. Two parts of Portland cement mixed with 1 part of lime and 6 parts of sand give a mixture twice as strong as one made of 1 part of lime to 2 parts of sand, while the cost is nearly the same. Such a mixture, however, would be too porous for jointing drains with. Four parts of cement, 2 parts of lime, and 1J parts of sand would make a suitable mixture.