BOOK III. 



57 



over that one of the twelve lines called " diameters " on which the number 

 XII is inscribed at both ends. 



South. 



vt 

 H 



North. 



When the needle which is governed by the magnet points directly 

 from the north to the south, the number XII at its tail, which is 

 forked, signifies the north, that number XII which is at its point indicates 

 the south. The sign VI superior indicates the east, and VI inferior the 

 west. Further, between each two cau^dinal points there are always 

 five others which are not so important. The first two of these directions 

 are called the prior directions ; the last two are called the posterior, and 

 the fifth direction lies immediately between the former and the latter ; it 

 is halved, and one half is attributed to one cardinal point and one half to the 

 other. For example, between the northern number XII and the eastern 

 number 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 is 

 described by Theophrastus (see Note lo, p. 115.) The first authentic and specific mention 

 of the compass appears to be by Alexander Neckam (an Englishman who died in 1217), 

 in his works De Utensilibus and De Naiuris Rerutn. The first tangible description of the 

 instrument was in a letter to Petrus Peregrinus de Maricourt, written in 1260, a translation 

 of which was published by Sir Sylvanus Thompson (London, 1902). His circle was divided into 

 four quadrants and these quarters divided into qo degrees each. The first mention of a 

 compass in connection with mines so far as we know is in the Niiizlich Bergbiichlin, a review 

 of which will be found in Appendix B. Thisjbook, which dates from 1500, gives a compass much 

 like the one described above by Agricola. It is divided in like manner into two halves of 12 

 divisions each. The four cardinal points being marked Mitternacht, Morgen, Mittag, and 

 Abend. Thus the directions read were referred to as 11. after midnight, etc. According to 

 Joseph Carne (Trans. Roy. Geol. Socv. of Cornwall, Vol. 11, 1814), the Cornish miners 

 formerly referred to North-South veins as 12 o'clock veins ; South-East North- West veins as 

 9 o'clock veins, etc. 



