DISCUSSION OF BAEOMETRIC OBSERVATIONS. 



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111 Table VI the first column contains 

 the names of the several years, from 1854 

 =^ to 1878, inclusive; the second column shows 

 the annual means of pressure, taken direct- 

 ly from the register. In order to eliminate 

 minor and irregular variations, the second 

 order of means of this series is taken, ana 

 this constitutes the third column. The re- 

 maining column contains Wolf's sun-spot 

 numbers, as given by Professor Loomis. 

 {Am. Journal of Science and Art^ April, 

 1873, p. 247.) As the numbers are there 

 given only through 1871, Professor Loomis 

 has kindly furnished me with those for the 

 subsequent years. The table indicates a 

 fluctuation of annual i^ressure, having a 

 range considerably in excess of the i)rob- 

 able error of a yearly mean. The years 

 1856, 1864, and 1870 are those of minimum 

 pressure, while maxima fall on the years 

 1858, 1866, and 1874. Hence the period 

 appears to consist of about eight years, 

 with no manifest relation to that of the 

 sun-spots. (See adjoining diagram.) 



Table VII shows the fluctuation of baro- 

 metric annual range. As the range of press- 

 ure attains its greatest extent each year du- 

 ring the winter months, the annual rangft 

 here considered is the difllerence between 

 the highest corrected reading of the baro- 

 meter in any one winter and the lowest 

 reading for the same winter; i. e., the year 

 in which each range is taken begins July 

 1 and ends June 30. The second column 

 of the table contains the names of the 

 months in which these highest and lowest readings occurred, the month 

 of the maximum being named first in each case. The two columns fol- 

 lowing contain the extreme values of pressure, and the next column 

 (the fifth) contains the range or difference between them. The periodic 

 fluctuation of the numbers in this column is so marked as to admit of 

 taking four orders of means, by which the accidental variations are elim- 

 inated. The result of this process constitutes the sixth column. The 

 seventh and last column contains the series of sun-spot numbers ; but 

 as the year to which any sun-spot number, as given by Wolf, belongs 

 has its beginning and end at January 0, instead of July 0, the sun-spot 

 numbers for this column are obtained by taking the first order of means 



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