BAROMETRICAL RULES. 19 



ing the weather, especially in such a country as is found along the 

 coast of Labrador. Barometers are of two varieties : the common 

 mercurial, where the air acts directly upon a basin of mercury in 

 which the inverted column of that same substance is placed ; and 

 the aneroid, where the atmosphere acts upon a metallic box, from 

 which the air has been exhausted, and by its pressure communicated 

 by a system of levers acts upon the needle to register the amount 

 of variance ; this is possible, since the column of mercury is 

 counterbalanced by the weight of the atmosphere. For a barom- 

 eter to be of the greatest use it must be read in connection with 

 the direction of the wind, and the temperature of the air, as shown 

 by the thermometer. The hours in the day when it stands highest 

 are at 9 a. m., and 9 p. m. ; and it is usually lowest at 3 a. m., and 

 3 p. M. These hours, therefore, are the best for making observa- 

 tions and are generally used by scientific men generally the world 

 over. 



The following table of rules will be found to apply in nine chances 

 out of ten, for the correct use or reading of the barometric needle. 



Rising barometer with south wind, — fine weather. 



Sudden rise, wind N. or N. N. W., in broken cold weather, 

 — rain or snow and sometimes nightly thaws. 



Rapid rise after S. W. gale and rain, — clear sky and sharp 

 white frost. 



Steady high pressure, wind strong W., — high temperature and 

 very little rain. 



Steady high pressure, wind strong E., — lower temperature and 

 sharp frost. 



FalHng barometer, with N. wind, — cold rain and storms in 

 summer, deep snow and severe frost in winter. 



Falling barometer, wind S., — more or less rain. 



Falling barometer, wind N. W., — cold rain in summer, severe 

 frost in winter. 



Falling barometer, high S. W. wind, — increasing storm. 



Steady and large fall, wind E., — wind S. or heavy snow or rain. 



Sudden and large fall, wind W., — violent storm N. W., or N. 



