154 ESSAY 



were almost always made on very short grass, 

 while Mr. Six's thermometers were laid upon 

 long grass bent, by strong pressure, towards 

 the earth ; in which state they marked a tem- 

 perature 1, 2, and 3 degrees lower, than that 

 shewn by similar thermometers placed upon 

 grass, less than an inch in height. Had it not 

 been for these circumstances, and the unfitness, 

 in various respects, besides the shortness of the 

 grass, for the production of a great cold, of the 

 common scene of my operations, I believe that, 

 in consequence of my thermometers being much 

 better adapted to mark a superficial, or transi- 

 tory cold, than those of Mr. Six, I should at 

 some time have seen a difference several degrees 

 greater, than the greatest ever seen by that 

 gentleman, which was one of 13j. In con- 

 firmation of this opinion, I shall mention, that 

 having, during a short visit to a more distant 

 part of the country, exposed, in the evening, a 

 thermometer upon the surface of an open grass 

 field, I found it soon after, although the grass 

 was short, and the weather warm, 14 lower 

 than a similar thermometer, suspended in the 

 air, 4 feet above the grass. If to this quantity 

 be added ^ a degree, on account of the dif- 

 ference in elevation between our suspended 

 thermometers, the cold, connected with dew, 





