MADE AT MARIETTA, OHIO. 



45 



The observations made with the old barometer between 1829 and 1832 show, 

 when compared with the succeeding record, a defect in the instrument most pro- 

 bably due to the presence of air above the mercury ; they were therefore omitted 

 in taking the monthly means which are given at the bottom of the table. The 

 means are derived from 27 years of observations (28 in November). They indicate 

 a regular progression, the maxima attaining their greatest value in January and 

 their least value between June and August (29.81 and 29.50 inches respectively), 

 and the minima attaining their least value in March and their greatest value in 

 August (28.78 and 29.12 inches respectively). 



Comparmg the annexed diagram with the corresponding one of the annual 

 inequality of the barometric extremes at Brunswick, Me., a close correspondence 

 wiU be noticed m the epochs and range of variation, though the curves are not so 

 regular owing to the shorter series of observations (27 years at Marietta and 50 at 

 Brunswick). 



Dtaobam" N. — Annual Inequality in the Barometric Extrenips. 



T 



In Table XV the monthly averages (of the extremes) and the ranges are given. 



Table XV 



. — Monthly Average and Range op Extreme Barometric Readings 





(at 32° Fah.). 





Average. 



Kange, 





Average. 



Eange. 



January . 





29i°.33 



0.i°96 



July .... 



29'°. 80 



0i"'.41 



February- 





.25 



0.89 



August .... 



.31 



0.38 



March 





.23 



0.89 



Septemlier 



.32 



0.55 



April 





.26 



0.74 



October .... 



.32 



0.70 



May 





.23 



0.56 



November 



.29 



0.85 



June 





.26 



0.47 



December 



.29 



0.92 



On the average the monthly means of extremes are 0'''.04 higher between July 

 and December than between January and June ; the amount is the same also at 

 Brunswick. 



The annual fluctuation in the range (difference of monthly extremes) is very 

 regular, but of smaller amount than the equally systematic results at Brunswick. 

 The monthly range is greatest (0.96 inches) in January, and least (0.38 inches) in 



