WATER 417 



or reservoir, fasten a piece of stout wire around the neck 

 of the bottle, remove the stopper, and retain it in the 

 hand. Then, using the wire as a handle, plunge the 

 bottle into the water, mouth downward, until it is 

 well beneath the surface ; then reverse it, allow it to fill, 

 and withdraw it from the water. Pour out a few cubic 

 centimetres of water from the bottle, 

 replace the stopper, and tie it down. 



(c) If the sample is obtained from 

 a lake, river or the sea ; or when it is 

 desired to compare samples taken at 

 varying depths, the apparatus de- 

 signed by v. Esmarch (Fig. 203) is 

 employed. In this the sterilised 

 bottle is enclosed in a weighted metal 

 cage which can be lowered, by means 

 of a graduated line, until the required 

 depth is reached. At this point the 

 bottle is opened by a thin wire cord 

 attached to the stopper; when the 

 bottle is full (as judged by the air 

 bubbles ceasing to rise) the puU on J r ' c V. itoi 

 the cord is released and the tension bottle for water 

 of the spiral spring above the stopper 

 again forces it into the neck of the bottle. When the 

 apparatus is taken out of the water, the small bottles 

 are filled from it, and packed in the ice-box mentioned 

 below. 



An inexpensive substitute for Esmarch' s bottle can 

 be made in the laboratory thus : 



Select a wide-mouthed glass stoppered bottle of about 

 500 c.c. capacity (about 20 cm. high and 8 cm. in 

 diameter) . 



Remove the glass stopper and insert a rubber cork 

 with two perforations in its place. 



Through one perforation pass a piece of glass tubing 

 about 5 cm. long and through the other a piece 22 

 27 



