S90 Prof. Barlow’s Experiments for determining the 
had already provided a pedestal or stand for the standard com- 
pass B, in a proper place in the vessel ; and, at a little past six 
o’clock in the morning, the Comet was swung round a buoy off 
Woolwich Dock-yard. The observations were made by two 
persons, one on shore, and the other on board, each having one 
of Gilbert’s patent azimuth compasses. At certain signals made 
on board, each took the magnetic bearing of the other, while the 
head of theAessel was successively directed to the several points 
of the compass ; and the difference in these bearings gave the 
local attraction at each point, at least as far as the tide would 
admit of her head being warped about the buoy. 
In this course of experiments, the counteracting power of the 
chimney was rendered very obvious, the local attraction having 
been found very inconsiderable, and just such as might have 
been predicted from the circumstance of elevating the common 
centre of attraction, as in the case of the iron-mast above men- 
tioned. 
These observations having been made at low water, we de- 
scended the river to North Fleet, and there lay by to repeat 
another set at high water. We now fixed up a second azimuth 
compass 9 feet abaft the boiler, and 15 feet 8 inches from the 
chimney, where it might be supposed the boiler would have a 
much greater effect than the chimney, and thereby bring the 
centre of attraction below the plane of no-attraction ; and, ha- 
ving thus engaged both our compasses, we made use of a theo- 
dolite on shore for taking the bearing of the stations on board, 
the zero of the fixed plate having been first carefully adjusted 
to the magnetic north. 
The vessel being now swung by the tide, with ihe usual 
arrangement of warps, &c., the following observations and re- 
sults were obtained. 
