NO. 13 FUNCTIONS OF RADIATION BRACKETT AND JOHNSTON 7 



the reflecting walls as indicated by the diagram in the lower half of 

 the top view. This arrangement provides that the central plant will 

 be symmetrically illuminated from four sides, and where four smaller 

 plants are used the distribution of radiation will not only be identical 

 for the different individuals but practically balanced so far as lateral 

 illumination is concerned. 



In this plan the overhead opening is particularly convenient for 

 the standard incandescent lamp. A suitable support which provides 

 for the raising and lowering of the lamp and reflector is shown in 

 the diagram. The lateral spaces, being long and narrow, lend them- 

 selves better to the discharge tube type of source. Where radiation in 

 the regions of the ultra-violet is desired the use of ultra-violet trans- 

 mitting windows presents such disadvantages, not only as to expense 

 but also as to loss of radiant energy, that provision has been made to 

 avoid them. In this case reflectors have been constructed which can 

 be bolted on in place of the lateral windows, making the entire enclo- 

 sure approximately a square with slightly rounded corners. In this 

 case the ultra-violet sources of radiation are introduced through holes 

 in the top, the only walls interposed being the transparent walls of the 

 discharge tube itself and such cooling jackets as are required. 



These special monel reflectors are shown on the right-hand side of 

 the diagram, the ordinary window arrangement being shown on the 

 left. In the latter case ordinary plate glass mirrors are inserted to 

 form the corner. Of course, in actual practice all four windows are 

 identically equipped, the diagram merely being a composite for con- 

 venience of illustration. 



CENTRAL CONTROL SYSTEM 



The central circulating system which has been developed for temp- 

 erature and humidity control is shown in Figure 3. For convenience 

 only one of the chambers is included. The location of the humidity- 

 control tank has been changed in order to permit a clearer diagram of 

 connections. The scale however is unchanged. A water-circulatmg 

 system provides for identical wall temperature of the four chambers. 

 From the lower central control tank thermostated to a temperature T\ 

 the water is pumped to the upper air temperature-control tank and 

 thence downward to each of the four chambers, returning to the 

 lower tank. Humidity control is secured by a similar recirculation of 

 air. It is pumped through a copper spiral in the upper temperature- 

 control tank T, thence through a central manifold into the various 

 chambers. It emerges near the loottom of the tank through an air-flow 



