Meteorological Observations at Hudson, Ohio. 311 



give the monthly averages of the observations, with such partic- 

 ulars as are thought most worthy of notice. 



BAROMETER. 



The mean diurnal oscillation is for the spring and summer 

 months 0.0405 ; autumn and winter months, 0.0463. Differ- 

 ence 0.0058. It is least of all in summer, and greatest in the 

 autumn. Average for the year, 0.0434. Prof. Forbes's formula, 



2;=. 1193 cos.-O — .0150, z being the oscillation in latitude 6, 

 gives for Hudson 2;=0.0435. The accordance is certainly re- 

 markable. 



The mean of all the above observations gives for the spring 

 months 28.751; summer 28.810; autumn 28.853; winter 28.809; 

 the mean pressure being .102 greater in autumn than spring. So 

 large a difference derived from three years' observations might be 

 regarded as indicating a law of nature. According to observa- 

 tions of fourteen years at London, the mean pressure was least 

 in spring and greatest in winter, the difference amounting to 

 .038. I have sought for information on this subject from other 

 barometric observations made in this country, but they are 

 almost without exception uncorrected for effect of temperature, 

 nor are any data furnished for computing it ; and even if the 

 temperature of the mercury were given, the barometers are 

 seldom to be depended upon, even for differential observations. 



