MAGNETIC DIPS IN THE UNITED STATES. HI 



one instance, at Schenectady, the difference amounts to 9 '.5; yet, for the entire 

 series of observations, the average excess of the results with one needle above 

 those with the other is only the tenth part of a minute, showing that the dif- 

 ferences in the partial results are accidental; and as these differences are not 

 very large, it is believed that the preceding observations furnish a tolerable ap- 

 proximation to the true magnetic dip at the places designated. 



