ON THE EFFECTS OF OCEANIC CURRENTS UPON CLIMATES. 



453 



If, instead of tabulating the mean annual temperatures, we tabulate 



From this table we see that the Grulf Stream adds nothing to the July 

 temperatures of the localities affected by it, but rather, on the whole, has 

 the effect of slightly diminishing- the summer heat. This fact will be of 

 extreme importance when we come to discuss the question of the Tertiary 



Climate of the Arctic Regions. 



3Iean Jumtary Tenvperatures. 



DifF. 



10°-22 F. 



14°-07 



21°-72 



37°-04 



40°-78 



19°-41 



From this table it is evident that the action of the Gulf Stream upon the 

 climates of high latitudes consists simply in raising the winter heat, while 

 the summer heat remains unaffected and the mean annual temperature is 

 raised by about half the amount of rise in the January temperature. 



The general climatal eflTect of the Gulf Stream is therefore to make 

 the annual range of temperature less ; ^ (the climate more insular), but 

 it has no effect whatever upon summer heat, or upon the fruiting of 

 plants and trees, that require a given July temperature for reproduction. 



These effects, as the table shows, reach a maximum somewhere about 

 70° N. lat. 



The two following tables show the effect that would be produced itpon 

 the mean July and January temperatures, at all longitudes by a supposed 

 withdrawal of the Gulf Stream, 



Ifean July Tempcrainres at all Longitudes. 



Mean 



- 0°-18 F 



This table proves that the effect of the Gulf Stream upon temperature 



> Longitudes (10° W. to 70° W.) are the Gulf Stream longitudes for 30° N. lat. 

 * This effect also diminishes the range of secular variation of temperatm-e, depend- 

 ing on the eccentricity and perihelion longitude of the earth's orbit. 



