Dr. Forry on the Climate of the United States, Si'c. 225 



tion — a deduction that the writer made several years ago — he 

 considers it exclusively his own. 



Reference may here be made to the " well established fact of 

 meridians of greatest cold" so called by Traill in the Encyclo- 

 poedia Britannica. " The remarkable fact," he says, " of the 

 influence of longitude on temperature leads to the conclusion, 

 that on each side of the equator there are two meridians, under 

 which the mean temperature is lowest. These have been term- 

 ed by Sir David Brewster the cold 'meridians, and their extremi- 

 ties are the poles of greatest cold. The position of these in the 

 northern hemisphere may be approximated from recent investiga- 

 tions ; and perhaps we shall not greatly err if we assign the lon- 

 gitude of 95° W, for the American, and of 100° E. for the Asiatic 

 cold meridians. The apparent coincidence of the cold meridians 

 with the general directions of Hansteen's lines of no variation is 

 perhaps more than accidental, when we reflect that there seem 

 to have beeri, in former ages, migrations of the cold meridians 

 eastward and westward, coincident, as far as we can judge from 

 recorded changes of climate in northern countries, with similar 

 migrations of the magnetic needle." 



This theory of cold meridians is at best extremely problemat- 

 ical. If there is any truth in the laws of climate as based on 

 physical geography, then is this theory no more than the " base- 

 less fabric of a vision." It is true that the meridians selected are 

 the coldest in some latitudes of the northern hemisphere, inas- 

 much as they traverse the interior of the continents, considerably 

 nearer the eastern or colder side. The longitude of 95° W. for 

 instance, passes nearly two degrees west of Port Snelling, Iowa, 

 which is very probably the coldest meridian in the United States ; 

 but as this same meridian passes through the Gulf of Mexico, the 

 result there at once explodes the whole hypothesis. And as the 

 same meridian continued into the southern hemisphere, traverses 

 the Pacific Ocean, the theory is again at fault ; for the laws of 

 climate resulting from physical geography place it about 30° far- 

 ther east on the continent of South America ; and in the old 

 world, the coldest meridian, if continued into the southern hemi- 

 sphere, instead of being that of 100°, will be found either in 

 Africa or New Hofland. But the circumstance of the migration 

 of these meridians, makes still greater demands upon our credu- 

 lity, inasmuch as it runs directly counter to the well established 



