340 



Scientific Proceedings, Royal Dublin Society. 



The complete apparatus used for these experiments is shown in the 

 photograph (fig. 4). The motor at the right of the picture drives the small 

 circulating pump (which is immersed in the water in the thermostat), and also 

 a stirrer in the thermostat. The water is pumped along the horizontal glass 

 tube to the left, and into the water-jacket of the apparatus already described, 

 from which it returns to the thermostat by the rubber tube from the top. 



To the extreme right will be seen one of a series of horizontal pulleys 

 which were connected to the small alternating current motor in order to 

 give the desired variation in speed of stirring. This pulley is connected to 

 the stirrer of the apparatus by the long belt appearing in the foreground, 

 thus imparting motion to the stirrer at a rate which could be determined by 

 the ratio of the various pulleys. The water circulation was continued, and 

 the stirrer run at a constant speed during the course of each experiment. 



Fig. 5. 



The lower speeds of revolution were counted directly, using a stop-watch to 

 check the time, and for the higher speeds the rate of one of the slower 

 moving pulleys was found and that of the stirrer by calculation. 



Five experiments were made with different rates of stirring, and one 

 experiment was made to compare the rate at which quiescent water absorbs 

 oxygen with the x'ates at which the thoroughly stirred water absorbs it. The 

 results of these experiments are shown in fig. 5. 



