Mr Forbes on Polar Temperature. 19 



but a second edition having appeared without any amelioration 

 in this particular, I cannot help pointing out, in i\\e first place, 

 the inexpediency (to use no stronger a word) of putting con- 

 clusions, purely speculative, against the weight of stubborn 

 facts ; and, in the next, I shall endeavour to show the fallacy 

 by which these two results have been set in opposition to one 

 another. 



I say nothing as to the general question of Mayer's empirical 

 law of climate ; I confine myself to the important assumption 

 to which its principal deviations from observation maybe traced, 

 that the mean temperature of the Pole is 32° Fahr., — an opi- 

 nion which Professor Leslie long maintained, and has only now 

 modified, by reducing it to 28° Fahr., — the freezing point of 

 sea-water. That in the time of Mayer such a position should 

 have been maintained, need not much surprise us, since few 

 observations had been made of the meteorology of the higher 

 latitudes ; but that in our own day, when Humboldt had shown 

 that the Isothermal line of 32°, passed between Lat. 65° and 

 71° in Europe, and as low as 53° in America ; * and above all, 

 when the direct experiments of our Arctic navigators had shown 

 that the mean temperature of the Pole must approach zero of 

 Fahrenheit nearer than 32°, some strong cause must be as- 

 signed for scepticism. The grand obstacle to the admission of 

 these truths is the supposed consequence of so low a tempera- 

 ture in increasing to an indefinite extent the accumulation of 

 ice in the Arctic regions, — an effect which has certainly not taken 

 place; for (as Mr Leslie justly remarks) the length of the 

 day would thereby be increased, which can be shown not to 

 have happened even to the most minute amount during the 

 last 2000 years. Now, taking up the question even at this 

 point, we have a right to call upon all who support the modern 

 system of inductive philosophy, to subject speculations to facts, 

 and, however singular might appear the stationary quantity of 

 Polar ice, to put into the class of unresolved phenomena the 

 low temperature of the Polar regions, determined during a 

 large portion of ^several different years, by Parry, and Frank- 

 lin, and Scoresby, and Lyon, and, least of all, attempt to avoid 

 the force of the cumulative evidence of registers, which metco- 



Mrmoiir* ttArceuil, tome iii. p. 625. 



