156 JOHN M. SMAIL. / 
Number of Experiments—8 
Duration of Experiments in days—44 
Average velocity of wind in miles per hour—12:0 
Volume of air entering sewer in cubic feet per minute—140 
Number of minutes taken to fill and empty sewer with air—31°5 
Number of times per day sewer was filled with air—46°6 
The result of tests made at shafts in Sydney and suburbs dur- 
ing the year is shewn by the accompanying tables, and they may 
be summarized as follows :— 
Area of districts in which sewers are ventilated—1667 acres. 
Total number of shafts erected—Induct 281, Exhust 630 
Number of miles pipe sewers ventilated varying in size from 
6” to 24” in diameter—69°16 
Number of miles brick sewers ventilated of various sizes—4°67 
The average work done by the induct shafts conducting air into 
the sewers varies from 1,397 cubic feet to 4,554 cubic feet per 
hour. ‘The foregoing results have been obtained from anemometer 
readings placed in the inspection boxes. The time occupied in 
taking each observation varied from eight to twenty minutes 
according to circumstances. The average wind velocity during 
the period occupied in testing was 8:43 miles per hour. The 
average work done shews that 1,579,656 cubic feet or 56°41 tons 
of sewer air is drawn from the sewers operated upon per hour. 
The quantity of air passed into the sewers, according to tests, 
is 857,400 cubic feet or 30°62 tons per hour. The oxydizing 
effect of this supply of pure air is. apparent when it is considered 
that twenty-one parts in every hundred is composed of oxygen. 
Factory shafts.—Factory shafts have been utilized for sewer 
ventilation with the cordial assent of the owners. The following 
summary will convey an idea of the aid rendered by the shafts : 
Cubic feet Cubic feet 
per hour. per day. 
1. Tooth’s Brewery, 9” connection .. 40,286 966,864 
2. Cameron’s Tobacco Factory, 6” con- 
nection utilizing exhaust steam... 95,369 128,856 
