i6 Captain Sabine’s experiments to determine the 
Mean of the preceding results. 
© i 
Experiment 1. 69 59, 7} 
Experiment 2. 70 05,8 1 70 04 N. dip. 
Experiment 3. 70 06,5) 
This was a nearer accordance with the direct observation 
with Meyer’s needle than I had anticipated. As this method, 
which is highly deserving of adoption in the lower magnetic 
latitudes, must become far less certain in parallels so high as 
70 °, when a very small alteration in either of the observed 
times will produce a wide difference in the conclusion : unless, 
therefore, the oscillation of a needle in suitable arcs can be 
continued through a number of seconds, much exceeding 
those of the preceding experiments, the result may be liable, 
without great care and frequent repetition, to considerable 
error. 
I am not aware that a method of deducing the dip on a 
similar principle, but possessing the same advantages in the 
high latitudes as the former does between the magnetic equa- 
tor and 45° (nearly), has been heretofore suggested : it is by 
observing the times in which a certain number of oscillations 
are made by the same needle in the following positions; first, 
when used as a dipping needle, vibrating in the plane of the 
meridian ; and, secondly, when suspended horizontally by a 
silk thread attached to either end of the axis, the needle being 
limited thereby to a horizontal motion. 
The square of the times of horizontal vibration being in- 
creased, as the radius to the cosine of the dip, it is obvious, 
that, as in the former method, the effect of errors of obser- 
vation on the result increases with the angle of the dip, 
