264 Professor Kaemtz on the more important 



of this, a sinking of the barometer is produced by the current 

 of air to the upper strata. The same must evidently take place 

 when the air above EF retains the same temperature, while 

 above AE and FB it is colder, or even when the temperature 

 above EF sinks a little, but at the same time sinks to a much 

 greater extent over AE and FB. The want of simultaneous 

 observations with the two instruments at very remote places, 

 renders the investigation of such deviations from the general law 

 more difficult to meteorologists ; but I have, on many occa- 

 sions, convinced myself of the accuracy of what has now been 

 stated. For example, the barometer has often sunk very much 

 in the west of Europe, and the temperature has at the same 

 time diminished, and in Germany a great cooling was combined 

 with a slight sinking of the barometer ; whereas in Russia the 

 air became very cold and the barometer rose exceedingly, so 

 that it was necessary for us to assume that the air must have 

 formed a current from the west of Europe. 



Although, therefore, the pressure of the atmosphere is con- 

 nected with the changes of temperature, yet we cannot term it 

 an ordinary thermometer, but must rather compare it to a dif- 

 Jhreniidl thermometer. It is well known to my readers, that, 

 in the latter, two balls are united by a narrow glass-tube, and 

 filled with dry air ; the air of both balls is separated by a drop 

 of quicksilver, or some other fluid placed in the tube, which can 

 move with freedom, and whose position can be read off on a 

 scale. Whatever temperature the two balls A and B may have, 

 the position of the drop remains unaltered, so long as the two 

 are only equally heated ; but if A be more heated than B, 

 then the drop moves towards B, in consequence of the expan- 

 sion of the air contained in A ; but this would also have been 

 the result if the ball A had preserved its former temperature, 

 while that of B had become lower. Thus, just as here, where 

 the movement of the drop only indicates that B is become colder 

 than A, without our being able to say with certainty if A has 

 acquired a higher, or B a lower temperature than formerly, so 

 we can only say, that a sinking of the barometer in EF merely 

 indicates that this part is warmer than AE and FB, which 

 might arise just as well from an unusual heating of EF, as from 

 an unusual cooling of AE. 



