BAROMETER. 



Fig. I. 



Fig- 1- 



A 



Fig. 3. 



V 



By an ingenious mechanism, Tor- 

 ricelli adapted to the siphon barome- 

 ter a dial {Fig. 2), upon which a nee- 

 dle indicates the movements of the 

 mercury. This instrument, which is 

 quite common, can nevertheless be 

 consulted with advantage. 



The barometer ( Fig. 3) presents this 

 difference from the preceding, that 

 the tube, instead of being recurved, 

 plunges perpendicularly into a basin 

 partly filled with meroury. It is fix- 

 ed to a scale, graduated on one side 

 in inches and tenths. 



The mercury in the barometer is 

 seldom to be seen so low as 28 inch- 

 es, or higher than 30^. It indicates 

 as follows : 



. Very dry weather, hard frost. 



. Settled fair, settled frost. 



. Fair, frost. 



. Changeable. 



. Rain, snow. 



. Much rain, much snow. 



. Stormy weather. 



The straight barometer is better 

 than the weather-glass. In mount- 

 ains the mercury never reaches 30J^ 

 inches, but remain? alwavs at a dis- 



31 inches 



30i . . 



30 . . 



29J . . 



29 . . 



28* . . 



28" . . 



tance below, proportionate to the 

 height of the place above tlie level of 

 the sea. In foretellmg changes of 

 weather, the act of falling or rising in 

 the mercury is better than an inspec- 

 tion of its height. The following rules 

 by Mr. Walker are as good as any 

 e.xtant : 



1. The barometer rising, may bo 

 considered as a general indication that 

 the weather, comparatively with the 

 state of it at the time of observation, 

 is becoming clearer. 



2. The atmosphere apparently be- 

 coming clearer, and the barometer 

 above rai7i, and rising, show a dispo- 

 sition in the air for fair weather. 



3. The atmosphere becoming clear, 

 and the barometer above changeable, 

 and rising, indicate fair weather. 



4. The atmosphere clear, and the 

 barometer near fair, and rising, de- 

 note continued fair weather. 



5. Our prognostic of the weather 

 is to be guided relatively, thus : if, 

 notwithstanding the sinking of the 

 barometer, little or no rain follow, and 

 it afterward rise, we may expect con- 

 tinued dry weather. 



6. If, during a series of cloudy, 

 rainy weather, the barometer rise 

 gradually, though yet below rain, es- 

 pecially if the wind change from the 

 south or west towards the north or 

 east points, clear and dry weather 

 may be expected. 



7. The weather for a short period, 

 viz., from morning until evening, may 

 commonly be foretold with a consid- 

 erable degree of certainty. If the ba- 

 rometer has risen during the night, and 

 is still rising, the clouds are high and 

 apparently dispersing, and the wind 

 calm, especially if it be in or about 

 the north or east points, a dry day 

 may be confidently expected. The 

 same rule applies for predicting the 

 weather from evening till morning. 



8. The barometer should be ob- 

 served occasionally thrice in the day, 

 or oftener when the weather is 

 changeable, in order to notice wheth- 

 er the mercury be stationary, rising, 

 or sinking ; for, from this circum- 

 stance, together with the direction of 

 the wind and the apparent state of 



fi9 



