535 



The mists then gradually formed over the shorter grass of the pasture 

 fields, yet, unless when the fog was very thick, it never formed over 

 stubble fields (i. e. where corn had grown). It was further observed, 

 that at times when undrained or imperfectly-drained ploughed fields 

 had this mist, those that were better drained were free from vapour ; 

 moreover, the furrows or low places of a field were the spots on 

 which fogs first formed. 



Hedges, on the contrary, seem to have a repulsive influence on 

 fogs ; the author has seen a field in which the mist rose higher than 

 the hedges, but did not flow over or even touch them, but at length 

 poured out through the gateway in a long dense column. 



These peculiarities seemed to be owing either to the different tem- 

 peratures of different trees and vegetables, or of the soils on which 

 they grew, or perhaps to both. To determine this, the author has 

 tested as carefully as possible the temperature of various flowers in 

 comparison with that of grass, as well as that of different soils ; imi- 

 tating artificially the conditions of drained and undrained fields, so 

 that the observations might be made close together, and therefore 

 better comparable with each other. In this latter series, which is 

 not yet completed, and does not form part of the present paper, 

 daily records are made of the greatest heat and cold on the surface 

 of soils, sand, gravel, clay, &c., as well as above the ground, and 

 from 2 to 8 inches below the surface. 



The thermometers employed were constructed by Messrs. Negretti 

 and Zambra ; they are self-registering, and entirely of glass ; the de- 

 grees being engraved on the tube, and rendered more distinctly visible 

 by means of enamel at the back. Some of the instruments are of 

 very small size, in order that they may be placed within the tubes of 

 certain flowers. 



All the observations were carried on by myself at the Beeston 

 Observatory. 



At first the thermometers were placed over the growing plant, and 

 afterwards the flowers and leaves were arranged in bottles of water, 

 and either exposed to full sunshine, or placed in the shade, the 

 bottles being sunk in the ground to the level of the grass, filled with 

 a bunch of flowers, and the thermometers placed immediately over 

 them. 



With regard to the readings on the grass and on the common 



