330 Mr. Harvey's experimental inquiries relative to the 
being of a more delicate construction, and used in moderate 
weather. 
It was intended to have ascertained the intensities in ano- 
ther circle, exterior to the greater of those before mentioned ; 
and also to have determined the same, at a series of other 
points, so situated above and below the deck, as to fall in the 
surfaces of three concentric spheres surrounding the binnacle, 
and of which O should be the common centre ; but the wind 
having suddenly become fair, the ship was obliged to sail ; a 
circumstance much to be regretted, as her gallant commander 
took a great interest in the inquiry, and was most anxious to 
afford every facility for prosecuting the subject. 
Before closing these remarks relative to the Helicon, it may 
not be uninteresting to point out some analogies which have 
been traced, between the magnetic intensities observed on 
board her, and certain anomalies in the variation observed in 
Captain Buchan's Voyage of Discovery. 
It was remarked on board the Trent,* that when Walker's 
compass was placed on the starboard gangway, the variation 
was found to be 33° 52' W. ; whereas at the binnacle it was 
25°52 , W. By bringing the compass on the gangway nearer 
to the binnacle, the difference between those results was ob- 
served to decrease, and when it was placed on the compa- 
nion, between the binnacle compasses, it exactly coincided 
with them. 
A somewhat analogous change in the magnetic intensity, 
was observed on the deck of the Helicon. At the station G, 
on the starboard gangway, the intensity was found to be 
* Journal of Science, Vol. IX. 
