62 



MICRO-ORGANISMS IN WATER 



If the Abater is to be collected from a tap (filter or 

 other), the latter should be allowed to run for five or 

 ten minutes before the sample is collected. When 

 samples of well water are required care must be taken 

 that the water has been pumped for some ten or twenty 

 minutes previously, in fact to obtain a representative 

 sample pumping operations should have been going on 

 continuously for several hours, or even 

 da3^s, previous to its collection. (See 

 chapter on Bacterial Contents of Various 

 Waters, p. 102.) 



For the collection of samples at con- 

 siderable or at specified depths, the fol- 

 lowing apparatus devised by Miqnel may 

 be found of service : — 



It consists of a glass vessel M, of 

 about 50 c.c. capacity, the neck of which 

 is drawn out to a fine point and bent as 

 seen at P^, held in its place by metal 

 bands a a a, to which a weight P from 2 

 to 3 kilograms is attached. The whole 

 is suspended by means of a strong cord 

 graduated in metres, yards, or feet by 

 means of rings and knots. Punning 

 alongside of this cord a thread of copper 

 passes through the rings d d^ situated 

 s OF Water a metre or yard apart. Attached to the 

 end of the copper thread is a ring A, 

 which encloses the fragile neck of the 

 vessel. When the apparatus has been lowered to the 

 required depth, the neck is broken off by givino- a quick, 

 sharp pull to the copper wire, and the water rushes 

 into the sterilised and vacuous vessel. It is then drawn 

 up, and the depth carefully noted to which it has been 

 lowered. If the water is not to be immediately examined, 



liiiiil 



Fig. 12. — Apparatus 

 for collecting 

 Sajiples 



AT definite depths 



(Miqnel). 



