Examination of Melbourne Tap Water. 



71 



METHODS. 



All the samples of water were taken from one of the laboratory- 

 taps which is in constant use. The nearest large pipe is a 30 inch 

 main which runs from the Preston Reserv'oir along the Sydney 

 Road. From this about half-a-mile of 6 inch and 4 inch pipes 

 along Grattan and Madeline Streets lead to the branch which 

 supplies the laboratory. 



The water was obtained as nearly as possible at 4 p.m., except 

 on Saturdays and Sundays, when it was taken at noon. 5 c.c. 

 were mixed in a flat glass dish, 7 inches in diameter, with 50 c.c. 

 of nutrient gelatine. The plates were kept at 18°-20° C, and 

 examined after 48 and 72 hours. As far as possible the results 

 of the last count of the colonies were taken, but in some cases the 

 plates became liquefied in less than 48 hours. The average 

 number of bacteria per c.c. was found by dividing the total 

 number of colonies on the plate by 5. The observations extended 

 from 4th July, 1901, to 29th January, 1902. 



RESULTS. 



Table I. 

 Average of Each Month. 



Total number of observations 

 Average of organisms per c.c. 



199 

 154 



