1792. on philosophical geography. 157 



not been so generally understood, though it consti- 

 tutes a very material link in the physical knowledge of 

 the globe. 



It is hoped the following explanation of them will be 

 found satisfactory. 



The reader will please to recollect, that the sea and 

 land breezes which are so beneficial in all tropical re- 

 gions, are a temporary interruption, for a small ex- 

 tent only, of the general trade wind. It has been 

 fhewn (vol. vi. p. ) that these are occasioned by the 

 great variation that takes place between the heat of 

 the day, and the cooinefs of night in tropical regions. 



Our philosophical pupils will also recollect, that in 

 consequence of the inclination of the earth's axis to 

 the plane of the ecliptic, conjoined with its annual 

 and diurnal rotations, it so happens that the length 

 of the day must be invariably the same at the equator^ 

 throughout the whole year ; but that, on every other 

 part of the surface of the globe, the length of the day 

 is perpetually varying, so as to produce that diversity 

 of seasons which we call summer and winter ; and 

 that the difference between the longest and fhortest 

 day in any place goes on continually increasing with 

 its latitude from the equator, till you reach the poky 

 where the whole heat of the year is concentrated into 

 one day of six months duration, which we call sum- 

 mer, and all the cold is accumulated into one night of 

 six months, called winter, without any sensible inter- 

 ruption of either the heat or the cold, in these regions, 

 in consequence of the diaarnal rotation of the earth. 

 Hence it follows, that at the equator the great vi- 



jfbiiudes of heat and cold are occasioned by the diur- 



