220 



Methods of Field Manurial Trials. 



found to be necessary, at least in the experiments (which were 

 conducted during August and September), when the car was 

 stationary for any length of time. 



When all the available ammonia is used up, the solution 

 (from which the gas can be re-extracted) must be emptied and 

 replaced by fresh water, and the bottles must also be changed. 

 This latter operation represents one man's work for a quarter 

 of an hour. 



The refrigeration of the car depends solely upon the opening 

 and closing of the tap which sets the ammonia free. The 

 absence of ice and melting water also renders the air much 

 drier than in ice waggons. Besides, while the filling of these 

 latter waggons has to be done by opening the cars, through 

 a trap-door in the roof, the replenishing of the ammonia and 

 water is performed entirely outside. 



In the experiments conducted, the temperature of the car 

 was about 2 — 3 degrees Fahr. higher than that obtained by the 

 use of ice, but this was due to the tap not being fully opened. 

 It was found that 1 lb. of ammonia lowered the temperature 

 by the same amount as 3 lb. of ice. 



Details are not given concerning the relative economy, from 

 the pecuniary point of view, of the two systems, but in view 

 of the much smaller amount of ammonia required, it seems 

 probable that its use is cheaper than the usual method of 

 employing ice. 



The ammonia car always exhibited less variation in tem- 

 perature than the ice waggons, and seemed hardly affected by 

 changes in the outside air. 



\_Extract jrom Bulletin mensnel de F Office de Renseignements Agricoles, issued 

 by the French Ministry of Agriculture, May, 1903.] 



The Methods of Exact Field Manurial Trials. 



Dr. P. Wagner has published, in the transactions of the 

 German Agricultural Society, a detailed explanation of the 

 general principles which should be borne in mind in conduct- 

 ing manurial experiments in the field. The rules that he lays 



