A modern theory, propounded by Herr H. Wehner, to account for discordant axes of buildings, is based upon the belief that the early Freemasons for centuries possessed, and kept secret, a knowledge of the polarity of the magnetic needle. Should it be ultimately proved that the builders employed the magnetic compass, it is urged that we shall have, in the case of dated churches, a key to the variation of the needle, and, conversely, for those churches whose date is unknown, a guide to their age[558]. That other folk, besides the Freemasons, were acquainted with the compass, is indisputable. A commonly received opinion is, that the mariner’s compass was introduced to Europe from China about the twelfth century, probably through the medium of the Arabs[559]. Strong evidence has, however, been produced to show that the instrument was discovered independently, or “re-discovered,” in Europe. Among other writers who refer unequivocally to the compass is the Englishman, Alexander Neckham (died A.D. 1217), whose description of its properties, as given in two Latin treatises, is unmistakeable[560]. Hence, from the early thirteenth century, and perhaps much before that time, the compass may have been used. But were the builders cognizant of the declination of the needle, and did they make allowance for it? This is extremely improbable. Indeed, it is authoritatively stated that the variation with which we are familiar was discovered by Stephen Burrowes (A.D. 1525-84), when voyaging between the North Cape of Finmark and Vaigatch[561]. This voyage would give a date of about the year 1553. The determinations were afterwards made by Gillebrand, who was professor of geometry at Gresham College[562]. If, then, the compass had been employed by masons previous to A.D. 1553, we should have expected, from their ignorance of its declination, considerable diversities of alinement. For the changes in declination have been very remarkable. Particulars are available dating from the year 1580. In that year, the needle pointed 11° 15´ E.; in 1622, the angle was 6° E.; while in 1657, there was no declination. By the year 1692, a swing of 6° W. had been attained, this rose to 24° 41´ W. in 1818, from which time the variation has steadily diminished[563]. These figures show that from 1580 to 1818 the needle has varied in London by so large an angle as 36° (approx.), and one may reasonably suppose that during the two or three centuries preceding there were similar alterations. The use of the compass, together with ignorance of its declination, would therefore supply a very prosaic explanation of differences in the axial line of churches.