312 Meteorological Observations at Hudson, Ohio. 



According to observations for five years at Montreal, by Mr. 

 M'Cord, the mean pressure was greatest in autumn and least in 

 summer, the difference being .090. This coincides in part with 

 my own result. The fluctuations of the barometer are however 

 so great and seemingly anomalous, that observations need to be 

 continued for a long period to establish any general law. The 

 mean pressure at Hudson for the three years is 28.806 inches. 

 In order to appreciate the value of this result, we must compare 

 it with observations made at other stations. The following table 

 exhibits the mean pressure of the atmosphere at the places 

 named, according to M. Schouw, the heights being reduced to the 

 level of the sea at the temperature of 32° F., and corrected for 

 the change of gravity in different latitudes. The table is found 

 in the Comptes Rendus des Seances de I'Academie, 1836, i, 573. 



Place. 



London, 



Altona, 



Dantzic, 



Konigsberg, 



Apenrade, 



Edinburgh, 



Christiania, 



Hardanger, 



Bergen, 



Reikiavig, 



Godthaab, 



Eyafiord, 



Godhavn, 



Upenavik, 



Melville Isl. 



Spitzbergen, 



Baroin. 

 29:977 



.961 

 .952 

 .967 

 .950 

 .882' 

 .907 

 .841 

 .843 

 .654 

 .651 

 .721 

 .731 

 .796 

 .872 

 .862 



The depression of the barometer near the equator, as well as 

 in high northern latitudes, is strikingly exhibited by this table. 

 With this standard let us compare some observations made in 

 this country. The data for New York are furnished by Mr. 

 Redfield, Am. Journal, vol. xxxviii, p. 326. Those for Mon- 

 treal, by Mr. M'Cord, being the mean of five years' observations, 

 and those for Quebec by Mr. Watts, N. Y. Regents' Report for 

 1837, p. 223. The reduction to the level of the sea was compu- 

 ted by the formula of Laplace, Mec. Cel. vol. iv, p. 572, and 

 the correction for change of gravity from the formula H=H' 

 (1—0.0026935 cos. 2 *,) where H represents the height of the 



