Location of the Isogonic Lines. 



18:} 



same day. Then came the discovery of magnetic storms, and a 

 knowledge of the large oscillations of the needle that they occasion, 

 and of the effects induced by local attraction and atmospheric elec- 

 tricity. Yet during probably more than one-half of this entire period 

 we find little attention paid l>y practical men t<> this important matter, 

 and the records of both the colonial ami earlier State surveys contain 

 hardly any references even to the amount of the declination of needles 

 of the compasses used in surveying the public lands, and no study 

 seems to have been made of the annual, monthly, diurnal or hourly 



human race, for without it America had never been discovered, 

 Sir Francis Drake would never have sailed around the world, nor 

 Hendrick Hudson brought his ship to the mouth of our river and 

 made known to our ancestors the rich territory of New York. 



When Chinese caravans traversed the sandy deserts toward Tibet, 

 guided by the " magnetic carriages," whose floating needles pointed 

 out the way to the rich commerce of the south-west; when the clumsy 

 junks that had hitherto crept along the Asiatic shores, ventured out 

 to sea and brought back to the land of Confucius the spices of Java 

 and the wealth of India, the foundation was laid for that great com- 

 merce which feeds the millions of the present, and without which all 

 our boasted civilization and knowledge would be as limited as our com- 

 munications with foreign countries difficult or inconvenient. 



It is not material whether Marco Polo first brought the magnetic 

 needle into use among Europeans or whether Flavio Gioja originated 

 the compass of the mariner. It is not important whether we owe its 

 introduction from the east to the Arab sailors of the Mediterranean, 

 although it may be said, in passing, that the word azimuth, or prop- 

 erly it is claimed «ss U n,ii/ -still so much used in surveying— is Arabic, 

 its eastern origin substantiated by its reckoning all bearings from the 

 south. However it came, the magnetic needle is with us, and has 

 long been with us, and has affected in a most important manner nearly 

 all the boundary lines of property in the older States of our Union. 



