272 Professor Kaemtz 07i tlie more important 



necessary to distinguish two separate cases. For it may 

 either be required to determine previously, the character 

 of whole seasons, or to deduce the state of the weather for 

 some hours or days from the state of the meteorological 

 instruments. Regarding the first point, owing to the inti- 

 mate connection existing between all the different parts of 

 the atmosphere, an approximate solution would only be possible 

 if we were acquainted with the actual state of the weather over 

 a large portion of the earth. As this is not the case, the solu- 

 tion of the problem would be impossible, if the barometer did 

 not afford us some feeble hints on the subject, by means of its 

 property of acting as a differential thermometer. When it 

 stands unusually low, and at the same time exhibits great dis- 

 turbance, we may thence conclude, that other regions are very 

 cold, and that we shall not only very soon receive back a por- 

 tion of the air from them ; but also, that the weather will for 

 some time follow an unusual course. But more cannot be said 

 with certainty, as we cannot know at the moment of observa- 

 tion, whether this great cold has its position in the interior of 

 Siberia or of America. If the first is the case, then we may 

 soon expect north-east winds ; whereas west winds come from 

 America, and these bring us in winter a moist and warm air. 

 It is thus possible, that the same phenomena may be combined 

 with perfectly opposite kinds of weather ; but nevertheless, 

 when we pursue more attentively our observation of the move- 

 ments of the barometer after that great depression, we are able, 

 with some degree of probability, to advance somewhat farther. 

 Thus, when west winds prevail for a long time, the vane veers 

 gradually to the north and the barometer gradually rises ; but 

 if the place of the unusually great cold be situated in Siberia, 

 then usually the N. E. contends suddenly against the S. W., 

 the moment of the lowest depression of the barometer is indi- 

 cated by a violent rain, and the pressure of the air which had 

 previously diminished with rapidity, again increases just as ra- 

 pidly during the north-east winds. 



i.i It is indeed difficult to predict satisfactorily the character of 

 whole seasons ; but this difficulty is still further increased, when 

 we have to indicate, how the weather is to be at an interval of 

 a few hours ; and in this we must seek for the objection which 



