156 Transactions of the American Institute. 



every one of those surmises which, before experiments were made, 

 we only knew as the creatures of the imagination called up by logical 

 inferences. 



This first success flushes us with the consciousness of our power, 

 and our vision involuntarily expands from this room out over the great 

 earth itself, and we picture to our minds what would happen to this 

 bar of soft iron if it were carried from here southward, across the 

 equator into the southern hemisphere, and as we progressed on our 

 voyage we should frequently hold the bar in a vertical line and test 

 its magnetic condition. Here, in the northern hemisphere, we know 

 from the experiments just made that the lower end of the bar is of 

 north magnetism ; but if, when we had reached the equatorial region 

 of the earth, we should test the bar, should not the experiment show 

 that it was devoid of magnetism ? fur did not our experiments on the 

 great magnet teach us that when the bar was placed at right angles 

 to the axis of the magnet and pointed toward its center, the bar 

 remained unmagnetized ? and those conditions would seem to be 

 exactly repeated with the earth, supposing it a magnet, if we held the 

 bar upright on or near the earth's equator. Pursuing our voyage yet 

 more to the south, we enter the southern hemisphere and approach 

 nearer the point where we supposed the earth's north magnetic pole 

 to exist. Here this nearer pole should induce its opposite magnetism 

 in the lower end of the bar, which should now be of south magnetism, 

 which is opposite to that which it had when on the other side of the 

 equator. We cannot travel so far together and test all this for our- 

 selves, but I find that another man has also had this same vision, and 

 actually sailed with a bar of iron into the South Atlantic, there to 

 seek its reality ; for, fortunately for the completeness of my argu- 

 ment, I made a note of a curious paper on this point, which I once 

 found while studying the history of magnetic research, as contained in 

 the Transactions of the Royal Society of London. This paper is 

 entitled, " On the Tendency of the Needle to a piece of Iron, held per- 

 pendicular, in several climates ; by a master of a ship, crossing the 

 Equinoctial Line, Anno 1684." Let the mariner give his own evi- 

 dence : "All the way from England to ten degrees north latitude the 

 north end of the needle tended to the upper end of the iron and the 

 south point to the lower end very strongly. * * * In latitude 

 eight degrees seventeen seconds south and meridian distance from the 

 Lizard seventeen degrees thirty-five seconds west, the north point of the 

 needle would not respect the upper end of the iron ; but the south 

 point would still somewhat respect the lower end. * * * In 



