ALLISON — NOVA SCOTIAN METEOROLOGV. 301 



mometers, or their height above the level of the sea. Obviously, 

 their readings are constantly wrong, generally too low. It may be 

 argued, that if the readings be always made from the same instru- 

 ment, merely to test the condition of the atmosphere at the one 

 point, and not for comparative or scientific purposes, they serve the 

 end sought. But this is not correct, even with this small object 

 alone in view, for the temperature will always afreet the mercurial 

 column ; and as it cannot be kept regular to a degree, these simple 

 readings must prove erroneous. Thus, let the observed height of 

 the column be 29.750, and the attached Thermometer 70°, and 

 again, let the same observed height remain, but with temperature 

 reduced to 40° — which may easily happen in any room — and the 

 ordinary observer says that the pressure is the same ; whereas, if 

 the first instance be only 29-750 in realify, the latter observation 

 is .080 higher, or 29.830, else the Barometer could not retain its 

 apparent height with 30° reduction of temperature. Therefore, 

 when I speak of Barometrical Height, or Pressure of Atmosphere, 

 I mean with all corrections included, viz., instrumental error cor- 

 rected, temperature calculated at 32°, Fahrenheit freezing point, 

 and addition made for height above sea. Aneroid Barometers are 

 not used in Meteorology, as though very useful in measuring 

 elevation, they are very apt to get out of order without the observ- 

 er's knowledge, and their rate of error is uncertain, beside the 

 metal scale being unduly affected by heat, and they cannot be set 

 to a point to obviate the expansion and contraction. The mean 

 Pressure for the whole year at Halifax is 29.779, and this is near 

 enough to that of other parts of the Province for application to any 

 climatological purpose. The Barometer here has risen to 30.992, 

 and fallen to 28.455, but from 29.000 to 30.500 inches is the general 

 range, and readings outside of these limits are very rare. Our 

 Barometrical altitude is comparatively low for our Latitude, but the 

 weight of atmosphere is affected, like the other Meteorological con- 

 stituents, by our Peninsular position, and proximity to the great 

 ocean. Thus the mean Barometerin 1875, at Halifax, in Latitude 

 44°. 39' N., was 0.151 inches lower than that at the inland station of 

 Brockville in Ontario, in almost the very same Latitude — 44°. 34% 



