gS . REPORT—1858. 
The total number of earthquakes given with dates is 252, representing by 
twelve the mean annual number. He tabulates the proportional number for 
each month thus :— 
TasLe I],—Scandinavia. Relative frequency throughout the year. 
September. 
November. 
December, 
Propor- 
tional 
number. 
Wintericocit..... Satin bu re eee 
Spring sc. O15 nave Rees CeO te 
Simmer. FPO Sr aad 0°90 
Abe GO? MOS PISS SOUS eee 0°99 
And at the two months of each solstice and equinox— 
March and April......... eee ae 
dunband Palys. P28, 3 SUES 0°74 
September and October ..........0°95 
December and January .......... 1°36 
As to general direction of the observed or horizontal element of shock—it 
has in most instances traversed a line, with more or less divergence, stretch- 
ing away from Iceland; and there can be little doubt that this is the real 
line of propagation of the original pulses. 
Perrey, however, conceives that a mean or chief resultant direction of shock 
for each given seismic region may be calculated in the following way. Taking 
the mean frequency of shock =1, he finds for the eight principal rhumbs 
proportional numbers, as for example in the present case :— 
TABLE III. 
Rhumb, or direction Relative frequency in 
of shock. direction. 
We sCOur es Wt aunctaencaceendaces Raicaeuncegashsesaesies 0°73 
IN Tree AN ctosintenertaccecvccseasscessesdecsesbactee 1:09 
El Biass Nicer aancsemre consis cis ieckvcnies cavecsecnbecse 0°73 
Riser spi Ne WV sincwsehins <ctus ones sas, “pete nape ee 1:09 
PME EIRE sa weaaiiaressavacaysvediapbacactaencssstae 1-09 
Die Wet shaun tab aecndes saeop oe cmarens doc ce dexcncteapebien 1:45 
pple [ato duscatenass Wencespcunestadecaacesnaaa® 1:09 
ING Weyauos lis tecadedsccrscessearace Diconccasnes Sudsecae 0°73 
Then, considering the cause of movement in any given direction to be pro- 
portional in intensity to the number of times that it has acted in each ob- 
served direction, viz. as proportional to the preceding numbers, he treats 
these as the forces themselves given in magnitude and in direction, and 
compounds them for a single resultant according to Lambert’s formula. 
This process gives for Scandinavia a general resultant direction of pro- 
pagation of S. 22°30' W., and with an intensity or force represented by 
0°94. 
If we study this presumed direction with the Mercator chart before us, 
we find that the line is not very wide of that forming the general length of 
