ON DEW, &c. 167 



nights, the differences were 9 and 8. The 

 superiority of the heat of metals on grass over 

 that of the air, when it did exist, was evidently 

 connected with the temperature of the grass, 

 which they covered, and this again with that of 

 the earth under the same portion of grass ; for 

 this portion was always a little warmer than the 

 metal, but not so warm as the earth. 



On the other hand, metals, on which dew 

 was forming while they lay upon grass, were 

 always colder than the air. In like manner, if 

 one metal upon the grassplat were dewed, while 

 another similarly situated remained dry, the 

 former was always colder than the latter. 



When a metal lying on the grassplat became 

 dewed, the grass under it was always colder 

 than that under another metal, which was un- 

 dewed. 



A metal, while receiving dew, in consequence 

 of being elevated in the air, was always colder 

 than a similar metal, which remained undewed 

 on the grass. 



The greatest instances of cold, observed by 

 me on metals, occurred at times, when other 

 bodies near to them had become considerably 

 colder than the atmosphere. 



The cold, however, contracted by metals, 

 from exposure to the sky in a clear and still 

 night, was always less than that of other bodies 



