‘54 LOCAL VARIATIONS AND VIBRATIONS OF EARTH’S SURFACE. 
In observing other levels placed north and south, he found a 
diurnal motion with a maximum about noon, the north ends 
rising ; no annual change in these levels only amounted to 4°89” 
t and west it amounted to 28-08”. He mentions one 
transit nancial in which the east pier rose 23” and had an 
azimuthal change of 75”, and cn similar changes were observed 
he transit instrum ent at Bern 
At Polkova, on May 10th, 1877, at 4h. 16min. a.m., when M. 
Nyren was observing the level of the transit instrument, he saw it 
to move, and every 20sec. for three minutes the bubble 
fact - lh. 14m. earlier the great earthquake at Iquique took 
lac 
Mr. Darwin adds—“Our experiments with the plumb-bob, as far 
as they go, confirm the results of M. d’Abbadie and M. Plantamour, 
and we think there can be little doubt that the surface of the eart 
is in incessant movement, with oscillations extending from a fractal 
of a second to a year. 
“M. Plantamour speaks as though it were generally recognised 
that one pier of a transit circle rises during one part of the year 
and falls at another ; but if this be so throughout Europe, we must 
suppose that there is a kind of tide in the solid earth produced by 
climatic changes, the rise and fall of the central parts of continents 
must then amount to — vase: in ve rtical — = 
the changes of level on the easterly and west 
must be exactly opposite to one another. We are not aware that 
any comparison of this kind has een undertaken. The idea 
seems of course exceedingly improbable, but we understand it to 
Europe which rise during the warmer parts of the year. Now if 
this be generally true for Europe, which has no easterly coast, it 
it is not easy to see how the change can be brought about except 
by a swelling of the whole continent.” 
A subsequent part of the report refers to the work done in 
Italy in the investigation of earth tremors, where it has been 
proved that there are periods lasting from a few days to a week 
or even more, in which the soil is in incessant movement, followed 
by a comparative cessation of such movement ; this he calls a 
seismic period. In the rset or — the end of one of these periods 
there is frequently an earthqu 
These periodic motions are ialbnenoad by the state of the atmo- 
spheric pressure. M. Po — sn tributed the variations of the vertical 
to this course, and M. Rossi says—“During thre e years no mark 
depression of the hassles has occurred without having been 
immediately y preceded, — or followed by marked seismic 
move 
