April, '14] 



SHELFORD: MEASURE OF EVAPORATION 



233 



What is still more important is rate of flow, the effect of which is 

 given in Table II, where we note that for very low rates such as are 



TABLE n.— SHOWING THE RELATION OF EVAPORATION TO THE RATE OF FLOW AND TO RELATIVE 

 HUMIDITY UNDER THE EXPERIMENTAL CONDITIONS. TOGETHER WITH THE RELATR^E RATE 

 OF INCREASE OF EVAPORATION AND XTLOCITY. (0.52 METER PER SEC. EQUALS LI MILES PER 

 HOUR. 0.68 EQUALS 1.5; 0.10 EQUALS 0.2). THE EQUIPMENT IS NOT ACCURATE ENOUGH TO 

 MAKE THIS MORE THAN A GENERAL GUIDE. PRESSURE WAS NOT READ. 



used for ventilating cages, e.g., 0.026 meter per sec. gives .40 evapo- 

 ration, while 0.052 meter per sec. gives .75, nearly double the 

 evaporation at average humidity and room temperature. Evapora- 

 tion should accordingly be measured, not only on account of its 

 importance in connection with measured temperature and humidity, 

 but also on account of the fact that rate of air movement is not other- 

 wise measurable in terms which have bearing on the life processes 

 of organisms. 



Mr. a.- F. Burgess: The conclusion given by Mr. Shelford in 

 regard to the effect of moisture on the length of life of insects has 

 proved true in many experiments which we have carried on at the 

 Gipsy Moth Laboratory. In shipping live beetles from Europe and 

 Japan, high mortality is usually caused by the drying out of the pack- 

 ing material. In cases where the packing material is moist on arrival 

 the mortality is always low. The same principle applies in handling 

 breeding jars. 



Mr, L. M. Peairs : Have j^ou tables or other means of telling how 

 much of the results secured were due to chemical action? 



Mr, V, E, Shelford: I have not attempted to determine that, 

 and I do not mean by advocating the use of the atmometer that all 

 these things can be determined, but this is the best means of getting 

 at the total effect of all these agencies. 



Mr, C, Gordon Hewitt: It seems to me that unless Professor 

 Shelford in his great ingenuit}^ devises some machine to determina the 

 amount of evaporation, which is due to the activity and metabolism 

 of the insects, these studies will not lead us very far. We are dealing 

 with only one of quite a number of factors. 



Adjournment, 



