ADVERTISEMENT. 



In October, 1860, the Smithsonian Institution published as one of the 

 " Contributions to Knowledge" the Register of Meteorological Observations 

 made at Providence, R. I., by Professor Alexis Caswell, extending over twenty- 

 eight years and a half, from December, 1831, to May, 1880, with summaries. 



After the decease of Professor Caswell, manuscript containing additional 

 observations for sixteen years and seven months, to the end of the year 1876, 

 was placed at the disposal of the Institution, and it was decided by the Secretary 

 to publish summaries for the entire series. 



The original publication was carefully revised with a view of removing 

 errors which might have escaped detection, and the summaries were then brought 

 up to the end of the series. 



The form of tabulation adopted by Professor Caswell has been retained in 

 all cases, but at the end of each table notes have been added showing changes in 

 the hours of observation from those given at the heads of the several columns. 



The observations, the results of which are here presented, were made at the 

 residence of Professor Caswell, on College Hill, a few hundred feet north of 

 University Hall, Providence, at an elevation of a little more than one hundred 

 and fifty feet above tide-water in the river. The geographical position of Uni- 

 versity Hall, as determined by the United States Coast and Geodetic Survey, is 

 latitude 41° 50'.0, longitude 71° 23'.9 W. of Greenwich. 



The barometer used previous to May, 1847, was constructed with a flexible 

 leather bottom. It was a good instrument of its kind and gave average results 

 which are believed to be reliable. In May, 1847, this instrument was replaced 

 by an open cistern barometer, made by Mr. William H. Temple, of Boston, with 

 a micrometer screw for the adjustment of the surface of the mercury in the cup to 

 an ivory point. By means of a vernier the height of the column could be read 

 to the nearest hundredth of an inch. The interior diameter of the tube was 

 about three-tenths of an inch. In the reduction of the barometric observations 

 no account has been taken of capillarity. The reductions to the temperature of 

 32° Fah. were made by means of the Smithsonian Meteorological Tables. The 

 reduction to sea-level was based upon the result of direct experiment. 



Several different thermometers were used previous to April, 1857, but always 

 the most accurate that could be obtained. After April, 1857, the thermometers 

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