59° 58° 57° 56° 55° 54° 53° ^^° Sf ^.°° .•^,^° .^° ^'^° '^'°° '^f '^° . . .^ 



\ 



55° 54° 53° 52° 51° 50° 49° 48° 47° 



Figure 4— Surface isotherms for the period 16-30 April 1953. 



303589 O - 55 ( Face p. 8) No. 3 



