82 THE AMERICAN MONTHLY [May 



living- plants, including- bacteria, animals, and inorg-anic 

 matter in such a way that the result can readily be 

 weig-hed, the volume determined, the number of particles 

 counted under a microscope, and tables constructed to 

 show the yield of any g-iven area of water. This method 

 is applicable in the artificial propag-ation of food fishes 

 since it collects the microscopic plants and animals which 

 constitute the food of newly hatched fry. The suitability 

 of water for receiving- any fish is as much dependent upon 

 the microscopic food it contains as on its temperature. 



Malted Milk Lunch Tablets. — These lozeng-ers are 

 conveniently carried in the pocket and available on trips 

 when one is hung^ry, faint or exhausted. They contain 

 concentrated food representing- the nutritive elements of 

 milk and the cereals. Being- free from starch and cane 

 sug-ar they do not appeal to a disorded appetite. Other- 

 wise they would replace all kinds of candy and oug-ht to do 

 so in spite of that fact. The Horlick Food Co., Rachine, 

 Wis., send out sample packag-es to doctors, teachers and 

 editors free of charg-e. 



SCIENCE-GOSSIP. 



Sewage Purification. — At Barking-, Eng-land, there are 

 biolog-ical filter-beds. The measurement of purification at- 

 tained is taken (a) from the amount of oxyg-en absorbed; 



(b) from the amount of albuminoid ammonia g-ot rid of; and 



(c) the increase in the quantity of nitrates. By passing- 

 the sewag-e intermittently throug-h these filters and by al- 

 lowing- them to rest and become aerated between the 

 charg-es, it was found that a purification of from 41 to 85 

 per cent was obtained, the whole of the org-anic matter was 

 completely removed and an effluent fit to be discharg-ed 

 into rivers was obtained. The purification g-oes on at the 

 rate of 750,000 g-allons per acre of biolog-ical filter. At 

 Sutton, Eng-land, a little different process is used, the fil- 

 trate from one bacteria tank being- passed throug-h a sec- 



