42 



TEMPERATURE. 



obt<ai)iod witbiii a few hours of tlie cessation of a fairly strong blow from the north-west. 

 In this case the inversion is very small, if it exists at all, but the tendency to the forma- 

 tion of an inversion is shown by a practically constant temperature from the ground to a 

 height of 1,000 metres. No doubt if the ascent had been made a few hours later a more 

 marked inversion would have been found. 



7000 



6000 



5000 



4000 



3000 



2000 



-SCc 



-40"c 



-30c -20"c 

 Temperature 



Fig. 13. Upper air temperatures. 



-10 c 



The physical meaning of these observations is very simple. When a vessel containing 

 gas is heated at the base, convexion currents are produced and a thorough mixing of the 



