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 circum- 

 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 Encyclopaedia 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., 

 &c. 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 



