404 ; ALEXANDER BUCHAN ON THE 
An examination of the July lines will best show the character of this 
singular fact in the distribution of the oscillation in the summer of the 
northern hemisphere. The following figures will also present the point in a 
striking light :—- 
Lat. N- Long. W. Ogg stom 
° ‘ o ‘ nen. 
San Francisco, . 37 48 122 23 0:068 
Fort Churchhill, . 5 39 18 119 15 0°091 
Washington, : , 38 56 76 58 0:060 
Angra da Heroisma, . 38 36 27 15 0009 
Ponta Delgada, . 5 37 44 26 55 0:006 
Lisbon, P . ‘ 38 43 MK 0:036 
Campo Maior, ; ; 39 5 6 50 0049 
Zaragoza, . 5 ; 41 39 0 58 0:063 
Long. E 
Reggio, . . . 38 6 15 38 0:008 
Naples, : : : 40 52 14 14 0:027 
Corfu, 5 ; ‘ 39 37 19 55 0:020 
Tiflis, ° . 5 41 43 44 47 0°084 
Pekin, : : : 39 54 116 26 0°060 
At these places, which scarcely differ four degrees in latitude from each other, 
the differences of the oscillation are enormous,—the extremes being 0-091 inch 
at Fort Churchhill in California, and 0:006 inch at Ponta Dalgada in the 
Azores, the one being 15 times greater than the other ; or if a correction of 
0-007 inch be added to correct the latter approximately to the true oscillation, 
the oscillation at Fort Churchhill is still 7 times greater than in the Azores. 
In lower latitudes the differences, though not so great, are yet considerable, 
thus— 
Lat. N. Long. W. mes 
S ‘ neh. 
City of Mexico, . 19 25 SE) 5) 0-079 
Up Park Camp, Fanaa, 18 0 76 56 0:059 
Barbadoes, 135 59 40 0:046 
Cape Verd, , : 14 40 17 25 0°043 
Long. E. 
Kuka Lake Tchad, ‘ 12 52 WU 3} 0:095 
Aden, : : : 12 46 Abies 1a) 0°115 
Bombay, . : : 18 54 V2 OL 0-067 
Madras, ; A : 1355 80 70 0-115 
Fort Blair, . F F 11 41 92 42 0:065 
Here the extremes are Aden, 0°115 inch, and Barbadoes, 0°046 inch, the 
oscillation being less than a third in Barbadoes of what it is at Aden, though 
both places are very nearly in the same latitude. 
Looking a little more closely at the July oscillation with reference to the - 
Atlantic as compared with Europe adjoining, the strictly local nature of its 
amplitude is very striking, as the followimg mean oscillation at places situated 
in lines running in three different directions will show :— 

