292 niSTORY OF discovery relative to magnetism. 



The variation of the magnetic needle from the meridian, or its declination, as 

 it it5 called, was known before the time of Columbu?', to whom its discovery has 

 been generally ascribed. His son, Ferdinand, in the biography of his father, 

 written in Italian, and published at Venice, in 1571, relates that Columbus, on 

 the ]4th of September, (on the 13th according to Irving,; 1492, wlien he was 

 at the distance of 200 leagues from the isle of JPerro, first observed the deviation 

 of thd magnetic needle, "a phenomenon, which," as the recorder says, "had 

 never been observed before." Columbus found that at the dusk of evening the 

 needle, instead of pointing towards the north star, deviated about half a point, 

 viz., from five to six degrees towards the northwest, and on the following morn- 

 ing still more. Astonished at this discovery, he observed the needle for three 

 days, and found that the deviation increased the further he advanced to the 

 west. At first he did not call the attention of the crew to this phenomenon, well 

 knowing how easily they might be excited to revolt. The sailors, however, 

 soon became aware of the fact, and, on account of it, fell into the greatest con- 

 sternation. It appeared to them that the very laws of nature were changing as 

 they advanced on their adventurous career, and that they were entering into a 

 new world governed by entirely unknown influences. They saw the compass 

 losing its truthful character, and asked with alarm what would become of them 

 without this guide on the trackless inhospitable ocean? Columbus had to tax 

 all his ingenuity to appease their terror. He stated to them that the needle 

 does not direct itself strictly towards the polar star, but towards another invisi- 

 ble point in the sky, and that the variation of the magnetic needle was not due 

 to a change in the compass, but to the motion and the diurnal revolution of this 

 celestial point around its pole. The confidence which the sailors had in the 

 astronomical knowledge of Columbus gave weight to this explanation, and their 

 excitement was consequently calmed. Although, as we have seen before, the 

 deviation was known two hundred years previous to the voyage of Columbus, 

 it is, however, evident from the facts just related that he made another discovery 

 of not less importance, namely, that of the difference of the declination in differ- 

 ent places of the earth. 



We find more accurate notions of the declination of the magnetic needle, but 

 these arc as late as the middle of the seventeenth century. In the year 1541 

 the deviation of the needle from the meridian at Paris was found to be from 

 seven to eight degrees to the east; in 1550 from eight to nine degrees ; and, in 

 1580, eleven degi'ees and a half to the east. Norman, who first observed the 

 deviations in London, found it to be 11^ degrees in 1596, and Cellibrand, at 

 the same place, in 1034, four degrees towards the east. 



We have seen by what precedes that the magnetic needle does not point in 

 all parts of the earth precisely to the geometric pole of the globe, and also that 

 the amount of the deviation is not the same in all places. But it is important 

 further to remark that a magnetic bar, free to move in every direction, will not 

 remain stationary if placed in a horizontal position ; on the contrary, in the 

 northern hemisphere the north end of the bar will turn down towards the earth, 

 and in the southern hemisphere the south end will assume a similar position. 

 The bar will only remain horizontal in the region of the equator. The discovery 

 of this important property, which is called tlie dip or inclination of the magnetic 

 needle, has been generally ascribed to Robert Norman, (whose name has just 

 been mentioned in connexion with the variation,) an Englishman, an experienced 

 sailor, and, as William Gilbert calls him, an artist of genius. It is said the dis- 

 covery was made by Norman in the year 1576, but, according to authentic 

 documents, it was known as early as 1544 to George Hartmann, vicar of the 

 church of St. Sebaldus, in Nuremberg. Hartmann was in correspondence with 

 Albert, Duke of Prussia, one of those enlightened minds who recognized the 

 importance of the sciences even at their early dawn. Their correspopdence, com- 

 mencing in 1541, was principally on scientific subjects, but the letter, which is 



