1916, by Mr. Albert H. Rhett, C. E., entitled "The Water-Proofing of Structures Subject to Stress from Moving Loads and Temperature Variations." In it Mr. Rhett gives a short, chronological record of the various unsuccessful endeavors to produce an effective water-proofing for bridge floors, leading up to a successful one of his own. In concluding his interesting and valuable memoir he makes the following statement:

To recapitulate, then: The theory evolved, and which it was attempted to prove, is that, if a structure subject to moving load and temperature variation is to be water-proofed, it can be effected only through the medium of a membrane, incorporated in the floor, which fulfills these two conditions:

(1) The compound element of this membrane must, of necessity, he the eventual

factor upon which reliance is to be placed.

(2) The compound, to fulfill its true function, must remain water-proof, non-

hardening, elastic, coherent, and adherent at low temperatures as well

as high.