BACTERIOLOGICAL EXAMINATION OF WATER. 159 



can for oar purposes consider that it is between 6° and 

 8 C. It is therefore best to pack the samples in ice. 

 There are a great number of different kinds of appa- 

 ratus which have been recommended for this purpose ; 

 they certainly answer the purpose for which they are 

 intended, but they are not always easily, obtained. On 

 the other hand, a suitable apparatus, which is equally 

 convenient, may be easily made everywhere. Small 

 tins, such as those used for packing cocoa, containing 

 about from 100 to 250 grms., are selected, and in these 

 the test-tubes are packed with wadding, so that they 

 cannot be broken during transportation. The lids are 

 put on, and each tin is placed in a larger one of 500 

 to 1,000 grms. capacity, according to the size of the 

 smaller one. The larger tin should be prepared before- 

 hand for the reception of the smaller, by having 

 strands of strong wire bent into meshes and fastened 

 securely over its bottom and sides, so as to make a 

 safe support for the smaller one, and to keep it quite 

 securely in its central position in spite of even violent 

 shaking. The large tin is then filled with small pieces 

 of ice, as much water as is absolutely necessary to fill 

 it up is added ; some more bent wire is then placed 

 over the small tin, after which the lid of the larger 

 one is put on, and is carefully gummed down, so as to 

 prevent the water from running out. 



Even in summer the temperature inside the small 

 tin is sure not to rise over 6° C. in twenty-four hours. 



