The increasing use of concrete for tanks and reservoirs, and in various kinds of conduit and subway work It necessary thr.t trie concrete used for tliis piirposeshould be wst er-t if:^ht . Due to this inct a ^eat many more orless su,ccessful methods of v/f^tor-nrcof inf^, have been brouf:htinto practice. A study of v/ater-proof irif^ methods is beingmade Dy many enfjineers, in order to determine tlie one mostefficient for making: concrete impermeable. The purpose in this thesis is, first, to brinf^ together the most important facts concerning this subject as they have been determined by the experiments of others, and second, to give adescrirttion of tests performed by the v/riter for the purposeof determining the effect of v/ater-proof ing ingredients uponthe permeability of concrete.