CONTRIBUTIONS TO METEOROLOGY. 263 



Barometric Pressure. — The highest reading of the Barometer 

 during the year, was at 10 p.m., on the 22nd of January, and indicated 

 30.697 inches. The lowest reading for the same period occurred at 

 2 p.m., on the 21st of March, and was 29.021 inches, giving a yearly 

 range of 1.676 inches. The greatest monthly range was in January, 

 and this holds good for a series of years, with the exception of last 

 year, 1857, when December indicated the greatest monthly range. 

 June of the present year indicated the lowest monthly range, 0.660 

 inches, although July for a series of years has indicated the least 

 monthly range. This year July exceeded by 0.014 the lowest range 

 of June. The mean barometric pressure for the year was 29.829, 

 which exceeds by 0.071 inches the mean of last year, and shows an 

 increase in pressure of the atmosphere compared with a series of years. 

 The mean height of the barometer for the month of January was 29.907 

 inches ; for February, 29,809 inches ; for March, 29.804 inches ; for 

 April, 29.757 inches; for May, 29.751 inches; for June, 29.771 

 inches; for July, 29.759 inches; for August, 29.789 inches; for 

 September, 29.830 inches ; for October, 29.982 inches ; for December, 

 30.015 inches. The mean monthly range of the barometer for the 

 month of January was 1.627 inches ; for February, 1.129 inches ; for 

 March, 1.340 inches ; for April, 0.947 inches; for May, 1.039 inches; 

 for June, 0.660 inches; for July, 0.674 inches; for August, 0.714 

 inches ; for September, 1.221 inches; for October, 1.032 inches; for 

 November, 0.856 inches ; and for December, 1.241 inches. 



The greatest range within twenty-four hours, with a rising column, 

 occurred on the 21st January, and was 0.730 inches ; and the greatest 

 range, with a falling column, was on the 10th of January, and indicated 

 0.903 inches. The most sudden variation, with a rising column, 

 occurred on the 18th June, and from 3 p.m. to 3.20 p.m. {twenty 

 minutes) indicated a rise of 0.075 inches. The Symmetrical wave of 

 November exhibited but little fluctuation, the final trough terminated 

 at 6 a.m. on the 30th day. 



Temperature of the Atmosphere. — The mean temperature for the 

 year was 40°. 04 Fahrenheit, which shows a decrease in temperature of 

 0°.53 compared with the temperatrue of 1857, and indicates 1°.520 

 less than the mean temperature for a series of years. The lowest 

 observed temperature was on the 13th of February, and indicated 

 30°. 2 below zero. The highest temperature occurred on the 7th of 

 July, and was 99^.3, giving a yearly range or climatic difference of 



