and Laboratory Methods. 1675 



drop of (NH4)2S is to be added, the preparation inverted over a hollow ground 

 slide, sealed with oil, and placed under the microscope, when the spectrum will 

 show the hemochromogen band, disappearing on exposing the preparation to the 

 air, if blood is present. The band lies midway between the D and E lines. In 

 this way can blood be detected, with a 15mm. layer, in dilution of 1 of blood 

 to about 20,000 of water, or, with a 40 mm. layer, 1 in 40,000, involving of actual 

 blood about 5 to 100,000 c. c. The test can be safely made with no other optical 

 apparatus than a small, direct vision, pocket spectroscope, which can be inserted 

 into the microscope in place of the eyepiece, and a ^ or ^-inch objective. It is 

 not to be assumed, of course, that even the spectroscope accomplishes the now 

 impossible feat of distinguishing human blood from that of other mammals. 



In a paper on " Some Advantages of Pleld-Workon Surface Water Supplies," 

 Horatio N. Parker discusses the desirability of making periodical examinations 

 of water supplies, for the purpose of determining any change from the normal in 

 clearness, bacterial content, color, efficiency of filter beds, and other factors which 

 may affect the purity, portability, and appearance of water used for domestic pur- 

 poses. The author describes how the changes arise through natural or human 

 agencies, and indicates, in a general way, the remedies and their rhode of 

 application. 



" The Work of Mt. Prospect Laboratory of the Brooklyn Water Works " is 

 the title of a paper in which Mr. George C. Whipple, biologist and director, 

 describes the construction, equipment, and work of the leading water works 

 laboratory in America. The sources of the water supply of the city of Brooklyn 

 are so numerous and so varied in character that it was found several years ago 

 that its proper management would require much analytical work, both chemical 

 and biological. The laboratory was built in 1897, and has been constantly in 

 active operation since that time. The building contains rooms devoted to work 

 in chemistry, biology, and physics, as well as one for general purposes. The 

 staff consists of one biologist and director, one chemist, one assistant chemist, 

 and three assistants. Ihe amount of work accomplished may be judged from 

 the following statement : " The regular routine includes the bacteriological exam- 

 ination of three samples of water from the Ridgewood pumping station and from 

 a tap in the city, collected daily ; the complete physical, chemical, and biological 

 examination of nine samples from the distribution system, collected weekly ; the 

 physical, biological, and partial chemical examination of twenty-four samples 

 from the supply ponds, collected weekly, with complete chemical analyses monthly ; 

 the complete examination of nineteen samples from driven wells, collected 

 monthly ; and the complete examination of twenty-one samples from the private 

 water supply companies of Brooklyn and from the water supplies of the Borough 

 of Queens, collected quarterly. In addition to these regular samples, many extra 

 samples are taken at various times and places, as occasion requires. During 

 the two and a half }ears that the laboratory has been in operation this schedule 

 has resulted in the analysis of more than six thousand samples, as follows : 

 Samples received from July 12, 1897, to April 1, 1900 - 6471 

 Physical examinations .--..-- 5025 

 Complete chemical analyses ..---- 2562 



