1877.] the Lines of equal Barometric Pressure. 517 



/3,=0, taiiO = ±l, = 300° or 120°; 



for the isobar passing through M and D, 



/3^=/3^, tan0=ii|J; ^=228° or 48°. 



The following Tables contain the monthly mean barometric pressure 

 at G-reenwich for the eight years, and the corresponding values of 

 and (d.^. 



Taele I. — Monthly mean Barometric Pressure at Greenwich reduced 

 to mean Sea-level, 1842-1849. (Add 29 inches.) 



Month. 



1842. 



1843. 



1844. 



1845. 



1846. 



1847. 



1848. 



1849. 





in. 



in. 



in. 



in. 



in. 



in. 



in. 



in. 





1-082 



0-851 



1069 



0-882 



0-847 



0-918 



0-996 



0-949 





1-057 



0-651 



0-676 



1-021 



1-025 



0-963 



0-692 



1-285 



March 



0-923 



0-935 



0-886 



0975 



0-831 



1-066 



0-679 



1-093 





1-091 



0-861 



1-174 



0-870 



0-763 



0-828 



0-763 



0-692 



Mav 



0-955 



0-8.36 



1-119 



0-885 



0-951 



0-936 



1-097 



0-938 





1-070 



0-871 



0-984 



0-945 



1-034 



0-976 



0-812 



1-039 



July 



0-990 



0-996 



0-922 



0-939 



0-925 



1-092 



1-005 



0-958 





1-037 



0-988 



0-847 



0-899 



0-946 



1-046 



0-892 



1010 





0-885 



1-188 



1-052 



0-974 



0-994 



0-997 



1003 



0-937 





1-025 



0-778 



0-734 



1-021 



688 



0-976 



0-818 



0-918 





0-775 



0-893 



0-864 



0-750 



0-997 



1-080 



0-961 



0-919 





■1-184 



1-424 



1-066 



0-834 



0-877 



0-868 



0-983 



0-973 





1-006 



0-939 



0-950 



0-916 



0-906 



0-979 



0-892 



0-976 



Taele II. — Differences of the Monthly Mean Barometric Pressures at 

 Greenwich and at Makerstoun in thousandths of an inch. 



Month. 



1842. 



1843. 



1844. 



1845. 



1846. 



1847. 



1848. 



1849. 





+256 



+256 



+ 135 



+129 



+219 



+ 72 



+ 30 



+201 



Tebruary ... 



+206 



- 90 



. +115 



+ 73 



+ 170 



+ 96 



+262 



+226 





+201 



+ 34 



+118 



- 8 



+ 188 



+ 51 



+ 88 



+108 





- 93 



+138 



+ 132 



- 9 



- 9 



+136 



- 70 



+ 5 



May 



+ 95 



- 20 



- 99 



- 55 



+ 70 



+ 103 



+ 95 



- 93 





+ 75 



+ 19 



+ 125 



+117 



+100 



+ 73 



+ 106 



+ 71 



July 



+ 94 



-f-130 



+ 66 



+ 85 



+ 140 



+ 68 



+ 156 



+145 



August 



+ 84 



+ 99 



+127 



+ 90 



+ 26 



+ 63 



+ 135 



+121 



September... 



+ 1 



+ 20 



-}- 1 



+ 95 



+ 30 



+159 



+ 52 



- 89 



October 



+106 



+141 



+103 



+ 184 



+ 144 



+ 95 



+ 32 



+ 76 



orember ... 



+ 90 



+ 184 



+ 65 



+ 192 



+ 105 



+200 



+ 121 



+152 



December ... 



+299 



+223 



- 71 



+227 



+ 35 



+139 



+203 



+ 8 





+118 



+ 94 



+ 68 



+ 93 



+ 101 



+105 



+ 101 



+ 78 



2 p2 



