11 



isolate from soils. Mr. Goodey also devised a method for driving 

 the protozoa rapidly out of the soils, and so of enumerating them 

 directly. The method depends essentially upon the fact that when 

 an electric current is applied to a medium containing living protozoa 

 they travel with the current to the cathode. It was not found 

 possible to obtain ciliated protozoa in an active condition until 

 after the cultures had been incubated for from two to four hours. When 

 first observed they also had the appearance of organisms that had 

 just emerged from the encysted state, and contained no trace of food. 

 As two to four hours is also the time required for these ciliated 

 protozoa to emerge from their cysts, Goodey concludes that in any 

 normal soil the protozoa are not active but encysted, and therefore 

 cannot be effective in limiting the number of bacteria, as has been 

 suggested by Russell and Hutchinson. The investigation deals only 

 with the ciliated protozoa, and the amoeba in the soil may still have 

 the effect tliat Russell and Hutchinson attribute to them. Moreover, 

 under certain conditions of free moisture supply and temperature the 

 protozoa must become active, and these are also the conditions 

 whicli would make for the development of bacteria. 



A. L). Hall and N. H. J. Miller. ''The Absorption of 

 Atnmoiiia /roni the Atmosphere.'' Jour. Agric. Sci. 

 1911. 4, 5(>. 



This paper deals with a series of experiments on the rate of 

 absorption of annnonia from the atmosphere, when shallow dishes 

 containing dilute sul[)lmric acid were exposed close to the surface of 

 the ground and at 4 feet above it, in the Laboratory grounds, above 

 Broadbalk field and the grass field. The dishes were protected from 

 rain, and were also covered by line gauze screens to keep out the 

 flies and dust, which were found in the earlier experiments to 

 interfere seriously with the results. Determinations of the ammonia 

 absorbed were made every month, and the trials were continued for 

 two years. The amount of annnonia absorbed proved to be very 

 much less tlian had been obtained by previous investigators working 

 with similar methods, and there is evidence that this was due to the 

 exclusion of dust, etc., and perhaps to the diminished circulation of 

 the air over the absorbing liquid which was brought about by the 

 gauze screens. The dishes on the high level generally absorbed 

 more ammonia than those near the ground; this also is probably due 

 to the greater circulation of the air. The dishes in the Laboratory 

 grounds gave the highest returns, probably because of the proximity 

 of chimneys. The metliod however did not lead to any conclusions 

 as to whether the soil acts normally as an absorbent of annnonia 

 from the atmosphere, or whether it yields ammonia to the atmosphere. 



