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280 



METEOROLOGY. 



[Sect. IX. 



prepared will be greatly advanced by the zero points of 



ail barometers being referred to one common standard - 



Upon the arrival of the vessel in England, at the ter- 

 mination of the voyage, the ship's barometer should he 

 again compared with the same standard with which it 



T ■ 



was compared previous to sailing ; and should any differ- 

 ence be found, it should be most carefully recorded. 



Tlie correction for the height of the cistern above or 

 beloiv the water-line is additive in the former case 

 subtractive in the latter* Its amount may be taken 



nearly enough, by allowing 0*001 in, of the barometer 



for each foot of difference of level. 



An example of the application of these several cor- 

 rections is subjoined : — 



Attached Therm. 54'^' 3. 



Data for the correction of the 



Instrument, 



Barometer reading 

 Corr. for capacity 



29*409 

 •Oi. 



>* I 



Corr. for capillarity . 



Corr. for temperature 



Corr. for zero and water- 

 line .... 4- 



29*392 

 »032 



29-424 



•068 



29-356 



Neutral point i . . . 

 Capacity ^ 



Capillary action . . + 



Zero to Rotal Society , 4- 



Corr. for altitude above 



water-line . ^ • + 



30»123 



•032 

 •03G 



004 



040 



A J'^rcgate 

 sea-level 



pressure at 



• . • . 29*396 



Thermometers.— 'Th^ observer should be furnished with 



a delicate and accurate thermometer, most carefiillv com- 

 pared with a perfectly authentic standard, at several tem- 



considerably, and of which the freezing 



tures 



point has been most scrupulously verified. This he should 



keep 



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a tht;rmometer of reference, and every 



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