34f4 Mr Forbes on the dejects of the Sympiesometcr, 



This table I have placed the last of the series, because the 

 heights it indicates are pretty regular, and approach to the 

 true altitude far nearer than any of the others ; and it is well 

 worthy of observation, that it appears to be the only instance 

 of the temperature of the lower station being equal to or 

 greater than that of the upper. This surely indicates some 

 permanent want of compensation of temperature. In this set 

 the thermometer generally falls, and the sympiesometer gene- 

 rally ascends to the conclusion of the observations. Some 

 small fluctuations not exceeding one or two hundredths of an 

 inch occur, and the oscillations of the thermometer, contrary to 

 the diurnal decline of temperature, do not exceed 0°.2 between 

 any two observations. 



I shall conclude these experiments by giving the results of 

 one of a very simple nature, in which the instrument was re- 

 moved from station A to one about a fathom lower (D,) an apart- 

 ment partly^ under ground, and with a pretty free exposure to 

 the changes of external temperature, it will serve to confirm 

 our former results. The instrument was ascertained to be ex- 

 actly at the same height some time after its return to station A. 

 The column Diff. in the following table merely indicates the 

 successive differences of the height of the sympiesometer. 



Table VIII.— /ww6? \^th, 1825. 



No. Stat. Hour p. m. Therm. Sympiesometer. Diff. 



