ON DEW, &c. 275 



a second time, with increased attention, my 

 wonder ceased. For, as the pans he speaks of 

 were large, and touched one another, and as all 

 the pans employed in India, for the making of 

 ice, widen as they rise from the bottom, like 

 our milk-pans, the thermometer, placed by him 

 on the straw, must have been secluded from all 

 view of the sky, and would therefore mark a 

 temperature much higher, than if it had been 

 laid, as in my experiment, upon straw fully 

 exposed to the heavens. On this, the second 

 night, therefore, I placed a thermometer under 

 the edge of one of the pans lying on the straw 

 bed, and found it some time afterwards 6 higher, 

 than a similar instrument upon a part of the 

 straw bed which was uncovered. Generally, 

 however, the difference was not so great. If 

 my pans had been large, like those of Mr. Wil- 

 liams, I should, no doubt, have observed more 

 considerable differences ; for, in consequence 

 of their smallness, I could not lay a thermo- 

 meter on the straw bed, so as to be fully screened 

 from the sky by the edge of any of them, with- 

 out its being almost in contact with the vessel, 

 every part of which was always colder than the 

 sheltered straw. 



Much dew formed in the course of this night. 

 The greatest difference remarked by me, during 

 it, between the temperatures of grass and of air, 



T 2 



