193 
‘ 
ascribe to earth-tremors, propagated from remote centres of 
disturbance. These movements were vertical oscillations of 
the magnets, which came on suddenly, and by which all the 
instruments were, in general, simultaneously affected. That 
they were not due to any sudden change in the direction or 
intensity of the magnetic force, is evident from the fact that they 
were in general unaccompanied by any changes in the mean 
position of the magnetometers, such as would result from a 
sudden magnetic disturbance. It appeared equally evident 
that they were not the result of any ordinary extraneous dis- 
turbing causes, such as currents of air; for, besides that the 
instruments are well protected from such influences, they fre- 
quently occurred at times of perfect calm, and when there was 
no movement within the Observatory. Under these cireum- 
stances it was difficult to avoid the conclusion that they were 
the effects of mechanical movements of the earth’s crust itself, 
which were too slight to affect the senses directly. Under 
this supposition, Dr. Lloyd stated that he had given instruc- 
tions to his assistants to keep a record of these movements; 
and that he was now in possession of a registry of them for the 
last two years, the times of which he hoped soon to compare 
with those of recorded earthquake-shocks, and thus to estab- 
lish or disprove the conjecture respecting their origin which 
-he entertained. 
The Chairman read some extracts from a letter he had 
received from Dr. Lappenburg, and presented to the Aca- 
demy, on the part of Dr. Lappenburg, of Hamburg, the volume 
of the Encyclopedia in which his Essay on Ireland is printed. 
DONATIONS. 
On some Roman Vestigia, recently found at Kirkley 
Shore, in Westmoreland. By Captain W. H. Smith, R.N., 
&e. Presented by the Author. 
Vestiyes of the Natural History of Creation. 5th Edition. 
Presented by Anonymous. 
Twenty-four Maps of the Geological Survey of Great 
