SURFACE ISOTHERMS 'C 



Philadelphia 

 Wilmington 

 Battimor* 



_Ld 



55* 



30* 



2'5''W 



so»w 



TO»W 



Fi^ire 7. — Monthly surfarr i!44>tli<>riii rhart. Ortiihcr 11—17, 20. W6*>. 



13 



