MAGNETISM. 163 



vation of the sea-coast. They gradually abandoned their 

 ancient timid and lingering course along the shore and ven- 

 tured boldly into the ocean. Relying on this new guide, 

 they could steer in the darkest night, and under the most 

 cloudy sky, with a security and precision till then unknown. 

 The compass may be said to have opened to man the do- 

 minion of the sea, and to have put him in full possession of 

 the earth, by enabling him to visit every part of it. 



Nearly half a century elapsed, from the time of this dis- 

 covery, l3efore navigators ventured into any seas which they 

 had not been accustomed to frequent. But in the course of 

 the fifteenth century, discoveries were made far beyond the 

 conception of all former ages. In the first voyage of Co- 

 lumbus, the Spaniards were struck with an appearance, not 

 less astonishing than new. They observed that the mag- 

 netic needle, in their compasses, did not point exactly to 

 the polar star, but varied toward the west ; and, as they 

 proceeded, this variation increased. This appearance, 

 which filled the companions of Columbus with terror, and 

 which still remains one of the mysteries of nature, is that 

 deviation from the meridian which is called the variation of 

 the needle. It is different in different parts of the world ; 

 being west at some places, east at others, and in parts where 

 the variation is of the same name, its quantity is very dif- 

 ferent. It is the same to all needles in the same place ; and 

 for a long time, it was thought to be invariably the same, at 

 the same place, in all ages ; but it was discovered, about tMc 

 year 1625, that it was different at different times, in the 

 same place. From subsequent observations, it appears, that 

 this deviation was not a constant quantity, but that it gra- 

 dually diminished ; and at last, about the year 1660, it was 

 found that the needle at London pointed exactly north. At 

 present the declination at London is about twenty-four de- 

 grees west. For some years, it has been nearly stationary ; 

 but it is understood now to be returning in an easterly di- 

 rection. Knowing the variation, or declination of the mag- 

 netic needle, that is, the angle which the magnetic meridian 

 makes with the meridian of the place, mariners are able to 

 sail by the compass with as much accuracy as if it pointed 

 exactly north. 



The inclination, or dipping of the magnetic needle, ex- 

 presses the property which the magnet possesses of inclining 



