406. =Declination of the Needle.=--The declination of the needle is its deviation from a north and south line. It is in comparatively few parts of the earth's surface that there is no deviation from this line to the east or the west. "True as needle to the pole" has become a proverb, and when it was first uttered it was supposed to be founded in strict truth; but modern investigation has shown not only that the needle varies in its pointing in different localities, but that it varies to some little degree in its variations. The declination of the needle was first observed by Columbus in his first voyage of discovery, and it occasioned great alarm among the sailors, who, as Irving states, "thought the laws of nature were changing, and that the compass was about to lose its mysterious power." Notwithstanding these and other observations of a similar character, no great account was made of the declination of the needle till the middle of the seventeenth century. But since that time extensive records of its declinations at different localities have been made, and tables and charts have been constructed exhibiting them. These declinations are not constant, but vary somewhat every day, from the influence, it is supposed, of the sun upon the earth. 407. =Dip of the Needle.=--It is found that in most parts of the earth, if a needle be balanced before it is magnetized, and then be suspended from the same point, it will not be balanced, but one end will dip downward. This fact was discovered by Norman, a London optician, in 1576. He found that the dip at London was toward the north at an angle of 72°. In pursuing the investigation of this phenomenon it was found that going from the north toward the equator the dip constantly lessened, until a point was reached where the needle was horizontal. Then, on going south of this, a reverse dip occurred, that of the south pole, and the farther south the needle was carried the greater was the dip. In the north, Captain Ross in 1832 came to a locality north of Hudson's Bay, in lat. 70° 5′ N., long. 96° 45′ W., where the magnetic needle, freely suspended, was in a vertical line. No such locality has yet been discovered toward the south pole.