Lovering on Magnetic Observations at Cambridge. 87 
the toil of midnight observation, and sacrificed to the cause of 
severe science the natural tendencies of their youth. How excel- 
lently the work was done will appear by an examination of the 
published results. 
A few words will be needed to render the Tables generally 
intelligible, but they are reserved for another place. I will take 
occasion, however, to remark now, that the Vertical-Force instru- 
ment has not satisfied any observer who has used it, here or 
elsewhere. This may be owing, in part, to thermometric distur- 
bances, though Professor Lloyd, its inventor, ascribes it to mechan- 
ical difficulties in its construction. He seems disposed, there- 
fore, to abandon the instrument altogether; and he has already 
contrived another, called the Inclinometer, for observing the same 
element. For the benefit of those who have not access to the 
“Proceedings of the Royal Irish Academy,” I will transcribe the 
valuable remarks of this distinguished observer and expounder of 
Terrestrial Magnetism, in his own words ;— 
“In order to know all that relates to the earth’s magnetic 
force, at a given place, observation must furnish the values of 
three elements. Those which naturally present themselves for 
immediate determination are, the intensity of the force itself, and 
the two angles (the declination and inclination) which determine 
its direction. We may substitute for these, however, any other 
system of elements which are connected with them by known 
relations. Thus, we have hitherto preferred to observe the decli- 
nation, and the two components (horizontal and vertical) of the 
intensity ; and, in general, the main considerations which should 
guide us in our choice are, the exactness of the observed results, 
and the facility of their determination. 
“In this point of view, the declination and the horizontal com- 
