Meteorological Observations at Hudson, Ohio. 313 



barometer in latitude i>, and H' the height corresponding to lat- 

 itude 45^. 



29.989 



29.919 



In the transactions of the Albany Institute, vol. ii, p. 156, the 

 zero error of the Quebec barometer is stated at +0.110 com- 

 pared with that at Montreal. It is presumed that this correc- 

 tion has been applied to the above mean result. The eleva- 

 tion of the Montreal barometer is referred to the tide-waters of 

 the St. Lawrence ; that of Quebee to the level of the St. Law- 

 rence. It is not known how far this exceeds the mean level of 

 the sea, but probably not much, as the tide is said to rise at 

 Quebec. As it is now clearly proved that the mean pressure of 

 the atmosphere at the level of the sea is not every where the 

 same, a most extensive field of inquiry is presented to determine 

 experimentally the law of its variation. In particular, it is desir- 

 able to know, whether over an elevated continent the pressure is 

 the same as at the same height over the sea in the same latitude. 

 In order, however, that observations may be of any value for this 

 purpose, they should embrace a period of several years, the zero 

 error of the instrument should be accurately determined, and 

 also the elevation above the level of the sea. 



The following table exhibits the instances, corrected for tempera- 

 ture, in which the barometer has risen above 29.25. Although the 

 barometer may have remained at this height during the period of 

 several successive observations, it is regarded as but one instance. 



Vol. xLi, No. 2.— July-Sept. 1«41. 



40 



