NEGEETTI AND ZAMBKA, HOLBOEN VIADUCT, E.G. 3 



value of the pressure of the atmosphere on each square inch of surface, near the 

 sea-level, about the latitude of 50 degrees. Nearer the equator this mean 

 pressure is somewhat greater ; nearer the poles, somewhat less. For common 

 practical calculations it is assumed to be 15 Ibs. on the square inch. When it 

 became apparent that the movements of the barometric column furnished indi- 

 cations of the probable coming "changes in the weather, an attempt was made 

 to deduce from recorded observations the barometric height corresponding to 

 the most notable characteristics of weather. It was found that for fine dry 

 weather the mercury in the barometer at the sea-level generally stood above 30 

 inches ; changeable weather happened when it ranged from 30 to 29 inches, 

 and when rainy or stormy weather occurred it was even lower. Thus, it became 

 the practice to place upon barometer scales words (Fair, Change, Rain, &c.), 

 indicatory of the weather likely to accompany, or follow, the movements of the 

 mercury ; and the instruments bearing them obtained the name " Weather 

 Glasses." 



COMPARISON 



OF THE 



ENGLISH AND METRICAL SCALES OF BAROMETERS 



AT ALL 



TEMPERATURES COMMON TO BOTH. 



Inches. 

 32 

 31 

 30 

 29 

 28 

 27 

 26 

 25 

 24 

 23 

 22 

 21 

 20 

 19 

 18 

 17 



BY F. F. TUCKETT, ESQ. 



Millimetres. 

 406-2656 

 380-8740 

 355-4824 

 330-0908 

 304-6992 

 279-3076 

 253-9160 

 228-5244 

 203-1328 

 177-7412 

 152-3496 

 126-9580 

 101-5664 

 76-1748 

 50-7832 

 253916 



B 2 



