for iheThei'momeler. 493, 



difference of elevation; vicinity to^ or distance from, the 

 seat; the intervention of mountainous and woody coun- 

 tries, intercepting the currents. of hot or coid air, from 

 lower or higher latitudes];; difference of soil, as to its 

 power of absorbintX, accumulating, or reflecting heat, &c. 

 All of which irregularities, however, it might perhaps be 

 possible to calculate and allow for. 



From the equator to 23^ degrees on each side of it, the 

 progressive variations in temperature differ somewhat 

 from the other latitudes ; this is allowed for in the columns 

 of the mean annual temperatures, and likewise in the 

 three succeeding columns, which may be considered as 

 emanations from ihe first. 



I shall now conclude by presenting the following Table, 

 {see next page) which exhibits a comparative view of the 

 spale of Fahrenheit's thermometer with jnine. 



JEocplanatlon of the four Columns, 



Nbta bene, — A is my proposed scale, having the zero at 

 mean temperature. 



B is Fahrenheit's scale, 



C is the centigrade measure, adapted to ci)lumn A. 



D is my former scale, having the zero at the point t 

 have estimated to be the greatest natural cold. 



The four additional points marked thus * are appropriate 

 to this climate, viz. the greatest degree of cold, which was 

 observed on the morning of December 25, 1 796 : and the 

 tivo greatest decrees of heat, viz. in the shade and in the 

 sun^ observed m the afternoon of July 13, 180S. — The 

 temperature of springs, means of course the constant tem- 

 perature of ordinary (nnmediated) springs, which in all 

 cUmates corresponds pr^^ty exactly with the mean annual 

 temperature of the place, which iu London is .51'9. 



N. B. Thermometers have a point marked temperate^ 

 viz. at 50 of Fahrenheit; but 57| is the tniddle point of 

 the scale, that being the mean annual temperature of lati» 

 tude 45t. Richard Walker. 



Oxford, May 31, 1810. 



f Hence it follows that in islands, particularly small j>Zti/;J*, surrounded 

 by a large extent of sea, the winters are warmer, and the summers colder. 

 than on continents. 



\ The winters in those parts of North America which have been culti- 

 vated, are much less rigorous now than fo.merly, principally in conser 

 quence of the destroying of forests, occ. which present several sources of 

 (:v|d, amoDgst vyhich tvap^ralwi'h no iucousiderablc one. 



Table 



