34 



SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 'JJ 



In round numbers, and probably within the errors of observation, 

 these may be taken as 2 per cent above in July, 191 7, i per cent above 

 in July, 1905, I per cent below in July, 1913, and 2 per cent below 

 in July, 19 10. 



In figure 28 are outlined the areas of excess and defect of pressure 

 in July, 191 7, when the solar radiation averaged 2 per cent above 

 normal. The areas where there was an excess of pressure are shaded, 

 while the areas of deficient pressure are unshaded and the lines of 

 equal departure are broken. 



Solar radiation two percent above normal — July 1917. 



Fig. 28. 



It is seen that over the great oceans outside the tropics the pressure 

 is in excess of the normal, while over the continents it is below 

 normal, except in South America. The greatest excess and deficiency 

 are marked by the words " Max." and " Min." respectively. Over 

 the North Atlantic and over North America these centers are in 

 the far north, averaging about 64° N. Over the remaining continents 

 and oceans the data are insufficient to determine the exact position 

 of the " Max." and " Min." except to the extent that they are con- 

 siderably to the north of the normal position of the high and low 

 pressure centers characteristic of those regions. In the equatorial 

 belt and especially between about 5° N. and 20° S., the pressure is 

 generally below normal. 



