The following Table shews the Variation as observed with and without the Plate, at different times during the Voyage.

Variation Variation]

Latitude. Longitude. Ship's Head. without the with the Time of obser

A single glance at this Table is sufficient, to perceive the very irregular character of the variations, as determined without the plate, and their close approximation to uniformity when the plate was affixed.

Extract from Journal of H. M. S. Griper.

H. M. S. Griper at Sea, 25th May 1823.

Lat. 69° 164 N. Lon. by Chr. 7° 54′ E.

P. M.

REMARKS, &C.

Fresh breezes and cloudy.

P. G. 4. Fresh breezes with a

head swell.

More moderate-set top

ditto P. G. Midnight, moderate, and

ditto

T. D.

Variation 2 points west.

ENE

E by N

N

8. Squally weather.

ENE

ditto

gallant sails.

ENE

Lat. observed at Noon, 69° 12' 10'' N.; Long. by Chr. 10° 14′ 15′′ E.

The preceding is a copy of an extract from the journal of the vessel, showing the courses, &c. as kept both by the corrected and uncorrected compass, and the amount of errors corrected by the plate.

The course, according to both reckonings, is shewn in Fig. 5, and the numerical results will stand as below:

Course and distance made good between the observations on the 25th and 26th of May, 1823:

The following table shews the local attraction of the Griper, as ascertained by swinging her at Hammerfest, and the second Table shews the same when the plate was fixed.

·Hammerfest, Latitude 70° 40′ N. Longitude 23° 45′ E. Variation 11°26′ W.

Compass Correct

Position or deviated Magnetic

Dip. 77° 15' N.

Local

of Snip's Bearing of Bearing of AttracObject. Object.

tion.

Head

Object

Object. tion.

Note. The dip is supplied by Captain Sabine throughout.

These results will be found fully to bear out the representation made of them by Captain Clavering to the Admiralty, who, in his letter to John Barrow, Esq. says, "Having been directed by their Lordships to make trial of Mr Barlow's plate, under Mr Foster's direction, I forward that gentleman's report, which it will be unnecessary for me to comment upon, farther than to acknowledge the extreme practical utility of, it, as found during the whole voyage; as when once fixed abaft the compass (thereby neutralising the effect of the iron on board), nothing farther was necessary than to allow for the variation of the place."

And, in his letter to the author, he says, after speaking of the great amount of the attraction in the Griper :

"Under such circumstances, it is obvious that the compass would have been altogether useless, (as indeed it has always been admitted to be in these high latitudes), but for your valuable correcting plate, with which, as I have already stated in my report, we found the compass to which the apparatus was attached as serviceable in these latitudes as in any other."

What is here alluded to is an advantage attending the plate beyond what the author had foreseen, viz. that it not only causes the compass to work correctly, but it also enables it te