20 Staten Island Association of Arts and Sciences 



RULES FOR PROGNOSTICATING THE STATE OF THE 

 WEATHER FROM THE BAROMETER 



1. After a continuance of dry weather, if the barometer begins 

 to fall slowly and steadily, rain will certainly ensue, but if the 

 fine weather has been of long duration, the mercury may fall 

 for two or three days before any perceptible change takes place, 

 and the longer time elapses before the rain comes the longer the 

 wet weather is likely to last. 



2. Conversely, if after a great deal of wet weather with the 

 barometer below its mean height, the mercury begins to rise 

 steadily and slowly, fine weather will come, though two or three 

 wet days may first elapse, and the fine weather will be more per- 

 manent in proportion to the length of time that passes before the 

 perceptible change takes place. 



3. On either of the foregoing suppositions, if the change im- 

 mediately ensues on the motion of the mercury, the change will 

 be permanent. 



4. If the barometer rise slowly and "steadily for two days to- 

 gether or more, fine weather will come though for those two 

 days it may rain incessantly, and the reverse; but if the barom- 

 eter rise for two days or more during rain, and then on the ap- 

 pearance of fine weather begins to fall again, that fine weather 

 will be very transient, and vice versa. 



5. A sudden fall of the barometer in the spring or autumn indi- 

 cates wind, in the summer during very hot weather, a thunder- 

 storm may be expected; in winter, a sudden fall after frost of 

 some continuance indicates a change of wind, with thaw and 

 train; but in a continued frost a rise of the mercury indicates 

 approaching snow. 



6. No rapid fluctuations of the barometer are to be interpreted 

 as indicating either dry or wet weather of any continuance; it 

 is only the slow, steady, and continued rise or fall that is to be 

 attended to in this respect. 



7. A rise of the mercury late in the autumn after a long con- 

 tinuance of wet and windy weather, generally indicates a change 

 of wind to the northern quarter and the approach of frost. 



