MAGNETIC DECLINATION AT TORONTO, ST. HELENA, AND HOBARTON. 559 
nature and character of the lunar magnetic influence. At Toronto the easterly 
elongations take place almost exactly at the hours of upper and lower culmination, 
and the westerly elongations at the intermediate hours of 6 and 18. At Hobarton 
the westerly elongations (which, as Hobarton and Toronto are in opposite hemi- 
spheres, may be regarded as corresponding to the easterly at Toronto) take place 
(speaking generally) about two hours after the upper and lower culminations, and 
the easterly elongations (corresponding to the westerly at Toronto) about two hours 
after the lunar hours of 6 and 18. At St. Helena, which is in the same hemisphere 
with Hobarton, the westerly elongations occur about two hours before the culmina- 
tions, and the easterly extremes about two hours, or rather more, before the hours of 
6 and 18. The differences in this respect at the different stations are a feature of 
such essential theoretical importance, that I should have delayed the presentation of 
this paper until it could have been accompanied by a similar investigation into the 
results obtainable from the five years of hourly observations printed in the first volume 
of the Magnetical Observations at the Cape of Good Hope, had I not the expectation 
that that portion of the task may be undertaken by Mr. Pierce Morton, who now 
conducts the magnetical observatory at that station. 
The entire amount of the variation, reckoned from one extreme elongation to the 
other, is at Toronto about 2/" ; at Hobarton about 20"; and at St. Helena about 10". 
The terrestrial force, retaining the magnet suspended horizontally in its mean position, 
may be taken approximately at Toronto at 3-54, at Hobarton at 4*5 1 , and at St. ITelena 
at 5 5/. It may be desirable also to state that the amount of the magnetic Declination 
at the period under consideration was, at Toronto 1°34' West, at Hobarton 9° 55' East, 
and at St. Helena 23° 25' West. 
The number of observations which have contributed to these results (exclusive of 
those omitted on account of disturbance) are, 38,398 at Toronto, 33,771 at St. Helena, 
and 33,578 at Hobarton; making, altogether, 105,747 observations. 
With the exception of marking the observations for the lunar hours to which they 
most nearly correspond, and the calculation of the constants in the formulae at To- 
ronto and St. Helena, the processes to which the observations received from the sta- 
tions have been submitted have been executed by Mr. John Magrath, principal 
Clerk in the Woolwich Office, assisted by Sergeant Charles Organ and Corporal 
Matthew MTlroy, of the Royal Artillery, employed in the office as military clerks. 
Woolwich, November 16, 1853. 
4 D 
MDCCCLIir. 
