Hot and Thermal Springs, 4"C, 265 



be just so large as to admit a common wine bottle. The bottle, 

 filled with water, stands on a piece of board, which is half an 

 inch smaller than the opening of the box. Over the bottle is 

 placed another piece of wood, which is held fast to the former 

 by iron wires, and to the upper board is attached a wire, which 

 is long enough for the observer to be able to reach it with his 

 hand. The space above the bottle is filled with a bad con- 

 ductor, for instance with tow, and the box is covered over with 

 a board, upon which some stones are placed to prevent the en- 

 trance of the rain water, and the whole is covered with moss to 

 preserve it from unauthorized observers. After the lapse of four 

 weeks the first observation may be made ; for in that time the 

 disturbances, caused in the thermometrical relations by making 

 the hole, will have entirely subsided. However, it cannot be 

 otherwise than advantageous to allow a longer time for the re- 

 storation of the equilibrium before the first observation. As at 

 the depth of four feet the temperature continues to rise uninter- 

 ruptedly from the minimum to the maximum, and to fall from 

 the latter to the former, monthly observations are quite suffi- 

 cient to give the yearly mean temperature. Indeed, there can 

 be no doubt that 12 observations made in this manner will give 

 a more exact mean than observations made three times a-day in 

 the air, without being made also during the night. 



I have found that, even where there is a difference of tempera- 

 ture of 22°.50 between the atmosphere and the water in the 

 bottle, the temperature of the air has no influence on that of 

 the water, during the first two minutes. But two minutes are 

 quite sufficient for a sensitive thermometer to assume the tem- 

 perature of the water,* 



In this manner I have observed the temperature of the soil, 

 since the 28th February 1835, in front of the chemical labora- 

 tory near Bonn and on the Lowenburg, which rises with a 

 steep ascent from the Rhine to a height of 1173 feet above the 

 other point of observation. The results of the first year of my 

 observations are as follows : — 



* In the spring of 1835, I requested the monks of the Monastery of St Bern- 

 hard to add similar observations on the temperature of the soil to their va- 

 luable meteorological observations ; but 1 have not yet heard whether my re- 

 quest has been attended to. 



