1820.] Mr. Dalton on Meteorology. 



Mean Height of the Barometer at Manchester. 



249 



Yrs. 



1794. 



1795, 



1796 



1797 



1798. 



1799 

 1800. 

 1801. 

 1802 

 1803, 



1804, 



1805, 



1806. 



1807. 



1808. 



1809. 



1810. 



1811. 



1812. 



1813. 



1814. 



1815 



1816. 



1817. 



1818. 



Mean 



Jan 



29-94 

 30-03 

 29-47 

 30-00 

 29-85 



9-74 

 29-26 

 29-59 

 29-73 

 29-55 



Feb. 



29-71 

 29 60 

 29-77 

 30-23 

 30-02 



29-49 

 2970 

 29-56 

 29-57 

 29-67 



Mar. 



29-86 

 29-76 

 30-04 

 29-94 



April 



29-80 

 29-71 

 30-02 

 29-77 



29-91,29-87 



29-66 30-09 



•77 

 ■85 

 ■SI 

 ■18 

 72 

 85 



29-57 

 29-52 

 |30-10 

 i29-S4 

 29-57 

 30-15 

 29-95 

 29-95 

 30-14 

 29-66 

 29-94 

 20-70 

 29-84 

 29-82 



2976 



May 



29 91 

 30-11 



29-70 

 29-78 

 29-96 



29-66 29-46 

 29-69129-41 

 29-6129 86 

 29-86 29-83 29-90 

 29-88 29-67 29-77 



29-62 

 29-6! 

 29-65 



29 



29 



29 



30 



.SO 



30- 



29^ 



30- 



29- 



.30- 



29- 



29- 



29 



29 



29 



29-81 



correct- 



'xp»n?'|29-82|29-84 



62 

 91 



-82 

 OS 

 •25 

 -12 

 •74 

 •18 

 88 

 23 

 86 

 77 

 82 

 68 

 54 



29 

 29 

 30 

 29 

 29 

 29- 

 29 

 29 

 30 

 .30 

 29 

 30' 

 29- 

 30' 

 29' 



29 87 



29-89 



29-81 

 29-95 

 30-03 

 29-85 

 29-95 



June 



29-97 

 29 80 

 29-89 

 29-83 

 30-01 



3\\U 



29-92 

 29-89 

 29-6ti 

 29-96 

 29-72 



29-80 

 29-78 

 29-88 

 29-68 



29-83 29-93 



86 29-96 



29-86 



29-86 



30-00 

 29-90 

 29-98 

 29-84 

 30-11 

 30-00 

 29-93 

 29-87 

 3001 



29-89 



30 

 30 

 30 

 30 

 

 29 

 30 

 30 

 30 

 30- 

 30' 

 29- 

 ,30- 

 29- 

 30- 



29-88 



II 



04 

 -15 

 07 

 -05 

 •98 

 20 

 05 

 06 

 J3 

 14 

 97 



29-57 

 299-^ 

 29-65 

 29-6 



29 86 

 2997 



29 83 

 29-96 

 29-98 

 29 -9^ 

 29-86 

 .'iO-18 

 30-07 



30 00 

 29-94 

 30-20 



02129-7' 

 ■2629-80 

 1230-15 



»z. 



29-84 

 29-89 

 30-09 

 30-06 

 30-08 



29-50 



Sept. 



29-78 

 29-99 

 29-90 

 29-64 

 29-75 



29-53 



29-8i 29-5^ 

 •.'9-88 29-73 



39-82 

 -'9-86 



29-98 



29-89 



29-95 29-85 



90 

 97 

 •87 

 •94 

 •93 

 ■SO 

 ■96 

 ■02 

 13 

 17 

 03 

 00 

 05 



29-85 

 29-87 



Oct. 



29-70 

 29-52 

 29-88 

 2981 

 29-63 



Nov. Dec. 



Mean 



29-64 29-88 29-83 

 29-70 29-82(29-85 

 29-8.3 29-92129-85 

 29-87 29-60|2y-8T 

 29-48 29-87i29-85 



29-6529-44 

 29 -62129 -55 

 29-58,29-54 

 29-87:29-36 



29-5229-61 29-80:29-61 



29-46j29-61 

 29-29;29-66 

 29-5529-71 

 29-4629-72 



16 29 



83130- 

 17 29 



29-94 



29-92 



•64 29-87J29 

 94 30-28|29 

 •95i29'75 29 

 9029-55 29 

 -7629-78129 

 •23!30-03!29 

 ■00 29-55:29 

 ■70 30-0129 

 5329 94 30 

 ■75 29-81 129 

 86 29-76 29 

 92 30-04 129 

 94 29-86|'29 

 II3O-O2I29 

 95:29-9130 



83 29-85 

 8029-92 

 55 29-88 



85 



-87 

 S2 



29-90 

 29-95 

 29 91 

 77 29-92 

 7929-94 

 07 29-87 

 -9029-99 



29-94 

 29-96 

 29-88 

 29-85 

 29-93 



29-80'29-7g!29-76 29-85 



29-90 29-S9|29-80l29-78 29-79 



In the above table, the means for each year are placed on the 

 right, and the means for each montli of the year at the bottom ; 

 by which we are enabled to judge whether any particular season 

 or month of the year is more liable than another, to have an 

 accumulation or deficiency of the atmosphere. It is evidently 

 only from a long series of years that we are entitled to draw any 

 conclusions of this kind. 



From an inspection of the above table, it is obvious that the 

 barometer appears to be higher in the summer than in the 

 winter months ; but this must arise in part at least from the 

 expansion of mercury by heat ; a correction, therefore, is neces- 

 sary on that account ; and the following table of temperature for 

 each month in the year, wilh the known expansion of mercury, 

 enables us to apply the pioper correction. The correction being 

 applied accordingly, we have the subjoined corrected heights 

 for each month. On looking over this corrected column, we 

 still jierceive the mercury higher in the summer months than in 

 the winter. The heights for March, April, May, June, July, 

 August, and September, are all at or above the mean ; and June 

 in particular possesses a marked superiority of one-tenth of an 

 inch above the mean. The heights of January, Februaiy, Octo- 



