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IV. Contributions to Terrestrial Magnetism . — No. XIV. 
By General Sir Edward Sabine, B.A., K.C.B., F.B.S. 
Received June 18, — Read June 18, 1874. 
In this paper ( i.e . the XlV.th Number of the “Contributions to Terrestrial Magnetism”) 
I have the pleasure of presenting to the Royal Society the second half of the Magnetic 
Survey of the Northern Hemisphere, of which the first half was presented by me last 
year and is printed as No. XIII. of my “ Contributions to Terrestrial Magnetism.” These 
two papers, taken together with No. XI. (appertaining to the Southern Hemisphere), 
embrace fully three quarters of the entire globe. 
The form in which the observations are collected in the two latest papers (No. XIII. 
and the present, No. XIV.) is the same, viz. arranged in zones of latitude, each zone 
beginning with the meridian of Greenwich, and passing eastward round the globe until 
the same meridian is again reached. In No. XIII. these zones were eight in number, 
being each 5° of latitude in breadth (excepting the last, which comprised also the few 
observations north of the 80th parallel). In the present paper the zones are four in 
number, each being 10° in breadth. 
Zone 1, comprehending from the equator to 10° N. 
Zone 2, „ „ lat. 10° N. „ 20° N. 
Zone 3, „ „ „ 20° N. „ 30° N. 
Zone 4, „ „ „ 30° N. „ 40° N. 
The statements in the introduction to No. XIII. regarding the different Magnetic 
Elements apply equally to the present paper ; it may, however, be remarked in addition, 
that while the observations of Force are fewer, a larger proportion of them were made 
by the observers in absolute measure, and have therefore not needed conversion ; the 
remainder have been converted by the same method of proceeding as that described in 
No. XIII. 
In the present paper corrections for “ secular change.” have been much more 
sparingly introduced. For this three reasons may be assigned : — the first being the very 
satisfactory one that a larger proportion of the observations are at dates differing by so 
few years from the Mean Epoch (1840-45) that any corrections on this account may 
well be dispensed with ; another being, that in this part of the globe more of the earth’s 
surface is covered by the ocean, and it has not been thought advisable in either paper 
to correct “ Sea Observations ” for differences of epoch (regarding these generally as 
less influential than differences of “ Ship’s Attraction ”) ; the third reason being of a 
MDCCCLXXV. Z 
