Lovering on Magnetic Observations at Cambridge. 151 
second crusade, have now been added, so that the whole enter- 
prise will not be concluded till the close of 1845. In this volume, 
which is published under the care of Mr. Sabine, the curves for 
all the Term-days are projected and placed side by side with the 
corresponding ones derived from the observations made at Cam- 
bridge and Philadelphia, on this Western Continent, and at Prague, 
in Europe. The simultaneous character of the American distur- 
bances is exceedingly striking; the magnetic impulse is felt over 
the whole continent. But Mr. Sabine concludes, from the data 
before him, that the same derangement does not always sweep 
both continents; and this difference will appear on an examina- 
tion of the beautiful plates with which the volume is enriched. 
We shall do him and -the subject better justice to transcribe his 
conclusion in his own words. 
“The correspondence which is so strikingly manifested in the 
fluctuations of the declination and horizontal-force in America, 
and which has its counterpart in the correspondence shown by 
the term observations at the different stations in Europe, is not 
found to prevail in any thing like the same degree between the 
curves of the two continents when they are exhibited in compar- 
ison. Nevertheless, indications are not wanting of participation 
in disturbances having a common cause. The character of the 
Term-day in respect to the degree of the disturbance by which 
the magnetometers are affected may always be derived alike, 
whether we view the European or the American curves: and 
instances are not infrequent of individual perturbations, common to 
both continents, having their culminating points at the same ob- 
servation instant.. These are sometimes disturbances in the same 
direction in both continents, and sometimes in opposite directions. 
On the other hand, there are perturbations, and occasionally of 
considerable magnitude, in the one continent, of which no trace 
