APPENDIX H. 



MAGNETIC OBSERVATIONS AND RESULTS. 



The following table of the magnetic dip (or inclination), declination (or varia- 

 tion), and horizontal intensity of various points along the route from Fort Leaven- 

 worth, via Fort Kearney, Fort Laramie, and the South Pass, to Fort Bridger, and 

 thence, via Camp Floyd, by my new more northern route, to Genoa, in Carson Val- 

 ley, will not be without interest and value to the physicist as well as surveyor. 



The instruments used and experiments resorted to, as well as the method of at- 

 taining the ultimate values of the magnetic elements, will be found stated in the fol- 

 lowing communication of Lieutenant Putnam, Topographical Kngineers, my assistant, 

 by whom the observations were chiefly made. The Jones unitilar magnetometer used 

 by us was the one Dr. Kane had with him on his second Grinnell expedition to the 

 Arctic Ocean, in search of Sir John Franklin ; and though it was not altogether such 

 in its form or capabilities as I could have wished, yet, for the reason that 1 could pro- 

 cure no other and there was not time to have one made, I could not do better than to 

 take it. For a paper on the mode of conducting the experiments with this instrument, 

 and with the dip circle (or inclinometer), as well as of obtaining the mathematical 

 value of the elements involved, which has been of great service to us in facilitating 

 our work, I am indebted to Mr. J. E. Hilgard, of the Coast Survey, whose zeal in this 

 branch of scientific research is not greater than his ability, and to whom I have now 

 to express my grateful acknowledgments. 



In comparing the declination by the magnetometer (converted into a declinome- 

 ter) and compass observations on Polaris, as given in the subjoined table, it will be 

 noticed that there is a considerable difference between the results obtained ; and that 

 in one instance (at Fort Bridger) it reaches as much as 2° 6' 50". At first I was dis- 

 posed to reject the declinations as shown by the declinometer altogether, supposing 

 that this great difference was owing to a defectiveness on the part of the instrument, 

 but perceiving, on examining the reductions of Dr. Kane's observations in the months 

 of January, February, and March, 1854, at Van Rensselaer Harbor, by Mr. Charles 

 A. Schott, assistant, United States Coast Survey, that he gives the following as a class- 

 ification of the daily ranges according to their magnitudes, I have come to the con- 

 clusion, as the observations were taken with a great deal of care, that the differences 

 have arisen doubtless from the observations by the declinometer having been taken dur- 

 ing the day, and those by compass during the night, in connection with the delicate 

 nature of the declinometer, and that the results, therefore, as scientific tacts, are worthy 

 of record. 



