428 



was experimentally ascertained for a period of several weeks in July, 

 1919, by allowing the air after leaving the humidifier to pass through a 

 hood which was slipped over the sensitive parts of a Friez hygro-thermo- 

 graph. The air was jiassed through a block tin pipe coil surrounding the 

 temperature-sensitive part, before passing into the hood entrance. This 

 apparatus then recorded the temperature and the humidity of this air 



Fig. 32. Showing the unit P for simulating daily rhythm, (U. I. V.). Cool- 

 ing water tank at the top with high drain at the left and siphon valve at the 

 right to remove all water in cleaning. The C-shaped shelf, air cocks, and one 

 thermostat with heater also appear in the drawing. 



