PROCEEDINGS OF SECTION H. , 691 
tank-flushes ; (g) overflows of trays under baths and lavatories ; 
(2) trays under slop-sinks and closets. 
Greatest dangers arise from intermittent wastes. Upper 
ends generally open. Difficulty in securing interception. 
Good drainage requires— 
I.—Proper conductors to convey away the waste products 
made with non-absorbent, non-corrosible material, and 
joints—of sufficient (not too great) size and fall, and self- 
cleansing form and easily accessible. 
II.—Proper interceptors to prevent dangerous matter entering 
or leaving the conductors. Made with non-absorbent, 
non-corrosible materials and joints. Two classes. Self- 
cleansing form as small as practicable for (q), (c), (2), 
where gases only require interception, but not so self- 
cleansing as to empty by momentum or suction. Non- 
self-cleansing and of full size for (4) where solids and 
gases require interception. As interception is generally 
maintained by water, the surface should be as small as 
possible to lessen evaporation. 
III.—Proper disconnection to prevent pressure in the 
conductor and aid in ventilation— consists in leaving out- 
let end of each section of conductors open to the air- 
generally discharging over open drains or over inter- 
ceptors. 
IV.—Proper ventilation to maintain interception, which 
might be destroyed by suction where conductors unite 
or strong flushes are used—and to oxygenise the inner 
surface of conductors and render products of decompo- 
sition innocuous. Upcasts should be carried well above 
roofs and chimneys. 
It is characteristic of intermittent drainage that the inlets are 
open, so that interceptors must be fixed at outlets or at junction 
with continuous drainage. In continuous drainage interceptors 
should be fixed as near the inlets as possible. 
Foregoing classification and notes especially useful as a basis 
of criticism, and for instructions to inspectors. 
10.—FACTS AND FIGURES RELATING TO 
VACCINATION. 
By A. J. Tayior. 
