Especial attention is called to the shallowness of the vault and the lightened labor of cleaning it out. The swinging door at the rear facilitated the sprinkling of dry soil or ashes over the contents of the vault, thus avoiding the necessity of carrying dirt and dust into the building and dust settling upon the seat. This privy was in use for nearly 100 years without renewal or repairs. When last seen the original seat, which always was kept painted, showed no signs of decay. Modern methods would call for a concrete vault of guaranteed water-tightness,[3] proper ventilation and screening, and hinging the seat. [3] Directions for mixing and placing concrete to secure water-tightness are contained in an article entitled "Securing a dry cellar," U. S. Department of Agriculture Yearbook, 1919; published also as Yearbook Separate No. 824, and obtainable for 10 cents from the Superintendent of Documents, Government Printing Office, Washington, D. C. [Illustration: Fig. 11.--Screening the approach to a privy. _A_, Raised platform with lattice sides, suitable for short distances, convenient and easily cleared of snow; _B_, walk hidden by lattice work; _C_, walk enclosed by an arbor.] [Illustration: Fig. 12.--A primitive vault privy in Massachusetts. Note the tight, shallow, easily cleaned vault. _A_, Brick vault 5 by 6 feet, bottom about 1 foot in the ground; _B_, water-tight plastering; _C_, rowlock course of brick; _D_, door hinged at top; _E_, door button; _F_, three-pane window hinged at top; _G_, passageway.] Working drawings for a very convenient well-built two-seat vault privy are reproduced in figures 13 and 14. The essential features are shown in sufficient detail to require little explanation. With concrete mixtures of 1:2:3 (1 volume cement, 2 volumes sand, 3 volumes stone) for the vault and 1:2:4 for the posts there will be required a total of about 2 cubic yards of concrete, taking 3-1/2 barrels of cement, 1 cubic yard of sand, and 1-1/2 cubic yards of broken stone or screened gravel. The stone or gravel should not exceed 1 inch in diameter, except that a few cobblestones may be embedded where the vault wall is thickest, thus effecting a slight saving of materials. CHEMICAL CLOSET.