28 Lovering and Bond on Magnetic Observations at Cambridge. 
nish the materials for a comprehensive study of this problem and 
enable us to determine with more confidence than can be reposed 
in the comparison of places not widely removed from each other 
the extent and the laws of what are now classed among the irregu- 
lar perturbations of the magnetic equilibrium. All attempts at 
induction now must be considered as subordinate to the final dis- 
cussion; but they have their purpose in indicating from time to 
time the direction to which the attention of observers should be 
particularly turned. To this end, an arrangement supplementary to 
the large plan was completed with Lieutenant Riddell for making 
simultaneous observations on the declination Magnetometer at To- 
ronto and Cambridge, at intervals of fwo minutes from 0" 45: to 
1" 45' P. M. Gott. M. T. Such observations were accordingly taken 
at Toronto for the assigned hour every day (Sundays except- 
ed) from October 23d to November 19th inclusive. Similar ob- 
servations were made in Cambridge at the same time. Professor 
Bache would gladly have been a partner to this project but an 
accident prevented him from being informed of it in season. An- 
other agreement was formed to observe every vibration of the bar 
during one hour from 9 to 10 P. M. Gott. M. T. for one week 
commencing with the 4th of January, 1841. Fig. 2d of Plate IID. 
exhibits the hourly curve for the 28th of October; the upper 
one being the Cambridge curve and the lower one the Toronto 
curve. Here it will be noticed that the changes of flexure in the 
two curves are generally coincident in time and when they vary 
the maximum difference does not exceed the interval between two 
successive observations.* The hour selected for the January obser- 
* While this Paper was passing through the press we received an account 
of the proceedings of the Irish Academy at a recent meeting, containing some 
remarks by Professor Lloyd on contemporaneous observations at short inter- 
