Deceiibkk 14, 1900.] 



SCIENCE. 



907 



corner spring strips to prevent breaking. 

 The packing boxes should be covered and 

 provided with suitable fastenings. 



Bottles for microscopical samples should 

 have a capacity of at least one quart, and 

 should be of clear white glass, but they 

 need not have glass stoppers. Bottles for 

 bacterial samples should have a capacity of 

 at least four ounces and should have wide 

 mouths and glass stoppers. Before use 

 they should be washed as described above, 

 and then sterilized with dry heat for one 

 hour at 160 degrees C, or in an autoclav at 

 115 degrees C. for fifteen minutes. For 

 transportation they should be wrapped in 

 sterilized cloth, or the neck should be 

 covered with tinfoil and the bottles put in 

 a tin box. When bacterial samples must 

 of necessity stand for more than twelve 

 hours before plating, it is preferable to use 

 larger bottles than four ounces. The gallon 

 bottle used for the chemical sample may be 

 sterilized and used for the entire analysis. 

 When samples are not plated at the time of 

 collection, they should be kept on ice at 

 not less than 10 degrees C. Portable ice- 

 boxes with separate compartments for the 

 ice and bottles may be sent by express with 

 satisfactory results. 



The allowable time that may elapse be- 

 tween the collection of a sample and the 

 beginning of its analysis cannot be stated 

 definitely, as it depends upon the character 

 of the sample and other conditions, but the 

 following limits are generally safe : 



Chemical analysis. — For fairly pure sur- 

 face waters, 24 to 48 hours ; and for normal 

 ground water, 48 to 72 hours. Polluted 

 water requires analysis within twelve hours. 



Microscopical examination. — For fairly 

 pure waters, 24 hours. If fragile organ- 

 isms, such as Uroglena, Synura, etc., are 

 present, immediate examination may be 

 necessary. 



Bacteriological examination. — Immediate 

 plating is always best, but seldom practi- 



cable. With fairly pure waters packed in. 

 ice, plating within 12 hours after collection, 

 will not introduce errors suflBcient to vitiate 

 the results. 



Physical Examination. — The physical ex- 

 amination includes observations of the tem- 

 perature, general appearance, color, tur- 

 bidity and the odor in hot and cold 

 samples. 



The temperature should be taken at the 

 time of collection, and expressed, prefer- 

 ably Centigrade degrees, to the nearest 

 0.5 degree. For obtaining temperature of 

 water at various depths the thermophone 

 gives the most accurate results. 



The general appearance of the water 

 should be determined by inspection in 

 strong light after standing several hours. 

 Substances remaining in suspension are 

 then classed as ' turbidity on standing,' 

 and substances settling to the bottom, as 

 'sediment.' The terms, none, very slight, 

 slight, distinct, decided, etc., may be used 

 for general work as described in the reports 

 of the Massachusetts State Board of Health 

 Where methods are used for expressing the 

 turbidity and suspended matters numeri- 

 cally, as is necessary with sewage and some 

 waters in some lines of work, the descrip- 

 tion of appearance may be omitted. 



At the present time there is no uniformity 

 in the methods of measuring turbidity or 

 suspended matter. The wire method, the 

 disk method, the diaphanometer method, 

 the gravimetric method, and the use of 

 standards of comparison all appear to have 

 their field of usefulness. It is desirable 

 that some system should be adopted for 

 making the results by the various methods 

 comparable, at least for those lines of work 

 of the same general nature. In the absence 

 of the necessary experimental data, your 

 Committee is unable to make a definite rec- 

 ommendation at present, although studies 

 now in hand will probably make this pos- 

 sible another year. 



