oe 
ON THE FACTS AND THEORY OF EARTHQUAKE PHENOMENA. 57 
The total number of earthquakes, classed by months, is as follows :— 
Adz 4 Seasons, Seasons, 
Northern. | Southern. North. Sonthe 
January ......... 627 19 
February ...... 539 14 
March’ ......... 503 9 1669 42 
April .........60 489 17 
os apgtonedatie 438 20 
MUNG) 0... a 428 19 1355 56 
RIMLLY A xen te tose 415 18 
August ......... 488 12 
September...... 463 17 1366 47 
October......... 5J6 25 
November ...... 473 32 
December ...... 500 21 1489 78 
Totals ...... 5879 223 5879 223 
Total of Catalogue for both hemispheres capable of mensual 
classification .......... CE eee OCS. eee 6102 
Total of unclassed, except as to annual date ............ 67 
Total number catalogued........ 6772 
of which, there are recorded by season only— 
PRINS. a rje05, a5 a= eT ae eae 6 
Summer..... Sh, Rae rr dace nes bs apr Bie / 
AMEN OAM sts, 2%, e7ar~ oy 16.0 a oferine airs, ay atesenen ab 
IWanter <7 ete. 6 2 ais ee halek Cees YS 
LOtales. 4 cuter oo 
January, February, and March have been taken for the spring of the 
Northern Hemisphere, and for the Southern, July, August, and September. 
From the commencement of Catalogue to a.p. 1700, the recorded earth- 
quakes in the northern hemisphere are to those in the southern, 940 : 21, 
or as 44°3: 1. Again, from a.p. 1700 to 1800, the northern are to the 
southern, 1883 : 57, or 33 : 1]; and from the year 1800 to 1850, or conclusion 
of the Catalogue, the northern are to the southern, 3076 : 145, or 21°2 : 1,— 
a further indication of the effect upon any such statistic record, of the march 
of human discovery, the last fifty years having brought into play the vast 
seismic regions of the Southern Ocean and South Pacific, before all but un- 
known. The observed earthquakes in the Southern Hemisphere may now 
be estimated at from 43 to 50 per century, or one every two years. (See 
Appendix, No. II.). 
Distribution in space. 
Such are, perhaps, all the legitimate conclusions that we can now come 
to on the distribution in historic time ; and we now proceed to the discussion 
of the Catalogue, with respect to their distribution in space upon the surface 
of our earth. The method adopted, was that of graphically reproducing 
the area of each recorded earthquake by the superposition of coloured tints 
upon a large Mercator’s map of the world. The map chosen for use was 
that arranged by J. Purdie, and published by Laurie, London, 1851,—the 
dimensions being 75 inches by 48 inches, which admitted, from its large 
