B84 . - REPORT—1858. 
of calculation, the author regards earthquakes experienced in different regions, 
separated by regions where the shock is not perceptible, as distinct one from 
the other, and reckons as an earthquake every percussion felt in a separated 
region. This new method of calculation increases the number of earth- 
quakes in the Ist table from 2735 to 3041, and in the 2nd table from 
5388 to 6596. The same law is again apparent in these two new tables, 
and also in the four other tables which the author forms by dividing the 
half century between 1800 and 1850 into two intervals, each of a quarter 
of a century, and by successively applying the first and second methods 
of calculation to the earthquakes of these two intervals. : 
“In the third method of computation, M. Alexis Perrey regards every shock 
of which an earthquake is composed as a distinct phenomenon, and registers 
it separately ; but he does not possess the documents necessary for this plan, 
because the number of shocks in each earthquake has not been accurately 
noted. The author has hitherto contented himself with considering in this 
manner the Table of 931 shocks felt in South America, chiefly in Arequipa, 
published by M. Castelnau in the 5th volume of his ‘ Journey through the 
Central Regions of South America.’ This table, without leading to results 
identical with those furnished by the other two methods, exhibits the fun- 
damental relation already manifested. Lastly, in the fourth method of 
computation, the application of which would often be very difficult, and 
which has not yet been attempted by M. Alexis Perrey, we are to con- 
sider as an unique phenomenon the number of shocks consecutively felt in 
the same country during an interval preceded and followed in the same 
country by periods of tranquillity. 
“To the nine tables formed by one or other of the three first methods of 
computation the author has added a tenth, formed by the first method, 
This only embraces four years, from 1841 to 1845, and contains but 422 
days of earthquakes. In spite of this comparatively limited number, the 
proportion of the figures appears the same. In all these tables we observe 
a marked preponderance in the number of earthquakes which take place 
upon days close to the Syzygies, over those which occur at the Quadra- 
tures. However, it is but a general law which can be observed in the state- 
ment of figures of which the tables are composed; and there are numerous 
exceptions. In order to weaken the force of these anomalies, and more 
clearly to exhibit the fundamental law, M. Alexis Perrey divides the 29). 
53%, of which the lunation is composed, into 12ths, 16ths, 8ths,~-and forms, 
by proportionate calculations applied to the ciphers of his different tables 
constructed on the solar days, the numbers which correspond to each frac- 
tion of lunation; he displays in all these new tables (excepting some 
anomalies of detail) the law of the predominance of earthquakes at the 
Syzygies, and thus confirms more and more his conclusion, that, for half a 
century, earthquakes have been more frequent at the Syzygies than at the 
Quadratures, M. Alexis Perrey has also studied, in the more or less exten- 
sive registers which assisted him to draw up his different Tables, the ques- 
tion, whether there exists any connexion between the occurrence of earth- 
quakes and the variable distance of the moon from the earth in traversing 
the different portions of her elliptical orbit. For this purpose he has cal- 
culated in each of his registers, and according to the different modes of 
computation employed to draw up the above-mentioned tables, how often 
earthquakes have occurred two days before and after, and upon the day of 
the moon’s perigee and apogee; and he has shown, in the numbers thus ob- 
tained, that the total corresponding to the perigee, in which the moon is 
nearest the earth, is greater than that corresponding to the apogee, in which 
