147 



Place. 



Series by Professors Bache and 

 Courtenay. 



Series by Professor 

 Loomis. 



Magnetic 

 Dip. 



Date. 



Magnetic 

 Dip. 



Date. 



Baltimore, 

 Philadelphia, 

 New York, 

 West Point, 

 Providence, 

 Springfield, Mass. 

 Albany, 



70° 58'.6 

 72 00.2 



72 51.7 



73 37.2 



74 02.8 

 74 10.7 

 74 40.1 



1834. 

 July 19, P. M. 

 July 25, August 4, P.M. 

 August 7, A. M. 

 April, May, June, July. 

 August 8, P.M. 

 August 10, A. M. 

 August 11, P.M. 



71° 50.3 

 72 07.1 



72 52.2 



73 27.4 



73 59.6 



74 06.9 

 74 51.3 



1839. 

 Sept. 25, A. M. 

 Sept. 23, A. M. 

 Sept. 9, A. M. 

 Sept. 5, P.M. 

 Sept. 19, P. M. 

 Sept. 14, A.M. 

 Sept. 4, noon. 



Professor Bache further remarked, that in regard to the results for 

 Baltimore, he had at first supposed that an error of a degree had 

 occurred in recording or transcribing the observations of one or other 

 series. The difference of dip between New York and Philadelphia 

 was nearly fifty minutes ; and it was, therefore, not probable that that 

 between Philadelphia and Baltimore should be only seventeen minutes, 

 according to the numbers of Professor Loomis as they now stand. 



On the other hand, the dip reported by Professor Loomis agrees 

 better with the determination of Professor Patterson at Charlottesville, 

 and of Lieutenant Wilkes at Washington. The discrepancy thus not 

 being easily reconciled, it is much to be desired that other observa- 

 tions should be made at Baltimore. 



The agreement of the results for New York, Providence and Spring- 

 field, is reasonably close ; though, if the diminution of dip in the inter- 

 val of the two series be considered, the agreement at New York will 

 not be so close. At Philadelphia, Professor Bache has ascertained by 

 recent experiments made for the purpose, that the difference between 

 Professor Loomis and himself might be explained by the difference in 

 the stations used ; there being considerable local attraction at one or 

 the other, though he had not yet ascertained which represented most 

 properly the dip due to the position of Philadelphia. The difference 

 at West Point certainly, and that at Albany probably, resulted from 

 using different stations for observation. Professor Courtenay had 

 found the magnetic dip at the middle of the plain at West Point, to 

 differ several minutes from that at his house to the west of the 

 plain. Professor Loomis had used a station near the steamboat land- 

 ing. At Albany, he had observed near the station formerly used by 

 Professor Henry in the Academy Park ; and as the dip found by him in 

 1839, was nearly the same as that found by Professor Henry in 1834, 

 the discrepancy between them might be considered as amounting 



