File:Scottish geographical magazine (1885) (14780943154).jpg

Identifier: scottishgeograph25scotuoft (find matches)
Title: Scottish geographical magazine
Year: 1885 (1880s)
Authors: Scottish Geographical Society Royal Scottish Geographical Society
Subjects: Geography
Publisher: Edinburgh, Royal Scottish Geographical Society
Contributing Library: Robarts - University of Toronto
Digitizing Sponsor: University of Toronto

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ed both India and Australiain one 90° section, and South America in another. Unfortunately,as I thought then, Ncav Zealand had to be separated from Australia andleft to lord it alone, supreme among the islands of Polynesia. But asthe NcAV Zealanders themselves much prefer it this Avay, this feature ofthe map need hardly call for our regret. In projecting the circumpolar Avorld doAvn to 25° N. Lat., it soonbecame evident that the attempt to croAvd the spherical area of aninverted IwavI on to a disc no Iwgger than the periphery of its rim, Avas afeat involving gi-ave error. To spread the boAvl out involved error inthe opposite direction. To include the bowls actual surface all on acircle somcAvhat betAveen the tAvo Avas a scientific solution, but oneinvolving serious distortion. Figure 6 shoAvs the actual globular area as seen on the gores of aglobe starting from the Pole and extending to 25° N. Lat.—that is,subtending a total angle of over 2 (90-25) or 130 degrees of arc. As mpolE
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ERROR EVERY30°OF LOAJO.- E>1-A.CK ACCUMULATED OR Total error - grey Fig. 6.—For explanation see text. 458 SCOTTISH GEOGRAPHICAL MAGAZINE. we recede from the Pole where everything is correct, the error increases,the black intervening spaces indicating graphically the exact proportionof error. The shaded portion of the disc shows these spears of errorgathered into one sheath, as it were—the total error. And one can seethat it is excessive. Now, if we imagine the gores to be elastic, and weconstrict the outermost ring of longitude (25° N, Lat.) until we havesqueezed in and therefore widened out their ends, we have achievedpietorially what is, when this feat is done mathematically, known as anequal-area projection. In other words, as we go south from the Poleand each parallel of latitude gets too wide in its periphery for the truth,we make compensation by shortening each degree or group of degreesof latitude also as we go south. In this Avay, the process that adds tothe truth of

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