56 Report on A. Perrey’s Researches relative to Earthquakes. 
which he called attention to the Notes on Earthquakes addressed 
to him of late years by the learned Professor of Dijon, and he 
has often mentioned at our meetings the relations mo be- 
tween the frequency of. earthquakes and the age of the moon. 
The cause of the interest connected with these volenibo is 
easily understood. If, as is now generally supposed, the interior 
of the earth is ina liquid or pasty state through heat, and if the 
globe has for its solid part only a crust comparatively very thin, 
the interior liquid mass must tend to yield like the surface wa- 
ters to the pean ose exerted by the sun and moon, and 
there must be a ter to expansion in the direction of the 
radius acts of hae eo bodies ; but this tendency encounters 
resistance in the rigidity of the crust, which is the occasion of 
fractures and shocks. The intensity of this catse varies, like that 
for the tides of pm ocean, with the relative position of the sun 
and moon, and consequently with the age of the moon: and it 
should also be noted, that as the ocean’s tides rise and fall twice 
in a lunar day, at periods dependent on the moon’s passing the 
meridian, so in the internal fluid of the globe, there should be two 
changes in a day, the time varying with the same cause 
Without entering now into-more details, it will be easily con- 
ceived, that if the mobility of the internal mass of the globe 
plays a part in the production of earthquakes, there must be some 
dependance, admitting of study, between the occurrence of an 
earthquake, and the circumstances which uinenee the action of 
the moon on the whole globe or on any place or portion of it, 
that is, the angular distance with the sun, its onl distance from 
the earth, and its distance from the meridian of the place, or in 
other terms, the age of the moon, the time of perihelion, and the 
hour of the lunar day. 
These considerations which have not escaped M. Alexis Perrey, 
have beyond doubt inspired the idea of the two-fold work which 
we have been charged to examine; and they have obtained for 
the views, the interested attention of M. Arago and many other 
men of science. ‘They have involved on the part of the author 
the determination of the precise date, and period of the moon, for 
each earthquake on record and even for each shock of which earth- 
quakes may consist—a work of vast labor; the researches have 
been now continued for several years and are still in progress. 
In the memoir of the 21st of March, 1853, on the relations 
between the frequency of earthquakes and the age of the moon, 
the author devotes the first chapter to the tabulation and the nu- 
merical transformation of the results of observation. 
He has conceived four modes of tabulating the facts. 
In the first method, followed in his memoir presented to the Acad- 
emy on the 5th of May, 1847, the author reckons as a day of earth- 
quake each those on which the earth has been shaken, whether 
