96 



COMPRESSED AIR INSTALLATION AT THE 

 MARINE LABORATORY. 



By LIONEL WOOD. 



In order to provide means for suitably aerating the tanks and 

 dishes throughout the Laboratory, an air-compressing installation 

 was fitted during the spring of this year. 



Considerable difficulty was originally encountered, it being 

 ajjparently impossible to obtam satisfactory and trustworthy data 

 as to the aeration of tanks, and it was found necessary to attack the 

 problem from first principles. All the installations about which 

 information could be obtained appeared to require a two horse- 

 power compressor to raise the pressure of the air to about five 

 atmospheres ; the air being then taken to small storage cylinders 

 from which it passed through a reducing valve at about 0*4 or less 

 of an atmosphere to tanks in the buildings. In this particular 

 instance it was considered that the running and capital cost of such 

 an installation would be too high, and an attempt was made to do 

 the work in a more efficient and economical manner without sacri- 

 ficing rehability. 



The aspirator principle was the original method adopted of 

 aerating the water in the main aquarium, effected by leading a fins 

 jet of water into a glass tube extending to the bottom of the tank. 

 The jet, as it impinged on the water in the tube, imprisoned large 

 quantities of air, carrying it down to the bottom of the tube, where 

 it arose in the form of minute bubbles. Air broken up in this way 

 presented a maximum surface to the water, and effected a solution 

 in the most rapid manner. At the same time, a considerable current 

 was set up in the tank, due to the air displacement. 



As this method of aerating by means of extremely fine bubbles 

 proved so satisfactory in the original scheme, trials were made to 

 reproduce the same results by means of compressed air. A small 

 nozzle, about | inch diameter, capable of use with various sub- 

 stances, was connected to a hand air pump and receiver. The 

 nozzle was lowered to the bottom of the tank and au* passed through 

 it, the pressure being measured on a gauge. Numerous substances 



