BOOK III.

57

over that one of the twelve lines called “ diameters ” on which the numberXII is inscribed at both ends.

South.

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w

North.

When the needle which is governed by the magnet points directlyfrom the north to the south, the number XII at its tail, which isforked, signifies the north, that number XII which is at its point indicatesthe south. The 'sign VI superior indicates the east, and VI inferior thewest. Further, between each two cardinal points there are alwaysfive others which are not so important. The first two of these directionsare called the prior directions ; the last two are called the posterior, andthe fifth direction lies immediately between the former and the latter ; itis halved, and one half is attributed to one cardinal point and one half to theother. For example, between the northern number XII and the easternnumber VI, are points numbered I, II, III, IV, V, of which I and

view of the subject. The lodestone was well known even before Plato and Aristotle, and isdescribed by Theophrastus (see Note io, p. 115.) The first authentic and specific mentionpf the compass appears to be by Alexander Neckam (an Englishman who died in 1217),m his works De Utensilibus and De Naturis Rerum. The first tangible description of theinstrument was in a letter to Petrus Peregrinus de Maricourt, written in 1269, a translationof which was published by Sir Sylvanus Thompson (London, 1902). His circle was divided intofour quadrants and these quarters divided into 90 degrees each. The first mention of acompass in connection with mines so far as we know is in the Nutzlich Bergbiichlin, a reviewof which will be found in Appendix B. This book, which dates from 1500, gives a compass muchlike the one described above by Agricola. It is divided in like manner into two halves of 12divisions each. The four cardinal points being marked Mitternacht, Morgen, Mittag, andAbend. Thus the directions read were referred to as 11. after midnight, etc. According toJoseph Carne (Trans. Roy. Geol. Socy. of Cornwall, Vol. u, 1814), the Cornish minersformerly referred to North-South veins as 12 o’clock veins ; South-East North-West veins as9 o clock veins, etc.