84 



Major Graham of the U. S. Topog. Engineers, and mentioned 

 that they confirmed those made hy himself. He added, that 

 they gave additional confirmation to the fact of a very consi- 

 derable local attraction at the different stations in Baltimore, 

 to which he had been led by comparing his own observations 

 with those of Professors Courtenay and Loomis.'* 



The observations of M. Nicollet were made with a dipping circle 

 by Robinson, of London, and with two needles. The stations of ob- 

 servation were at the second square, N. E. of the Washington Mon- 

 ument, (the station of observation of Professor Bache,) and in the 

 Botanic Garden of St. Mary's College. The times of observation from 

 9 A. M. to 12 M., and from 3 to 6± P. M. on the 28th of April, 1841. 

 The resulting dip at the first station, 71° 34. 9, and at the second, 

 71° 33'.8. 



The observations of Major Graham were made with a dipping circle 

 and two needles, by Gambey. The stations of observation were four 

 in number. No. 1 was N. 5° E. 363 yards from the centre of the 

 Washington Monument, and is supposed to have been the station oc- 

 cupied by Prof. Loomis. The dates of observation, June 9th, 1 to 3 

 P.M. and June 10th, 6| to 9§ A.M. The resulting magnetic dips, 

 were 71° 48'.4. and 71° 46'. 0, mean 71° 47'.2, agreeing very well 

 with the determination of Prof. Loomis, (71° 50'. 3,) after making an 

 allowance for the diminution of dip in the interval between the obser- 

 vations. 



Station No. 2 bore N. 45° E. from the centre of the Washington 

 Monument, N. 11° W. from the dome of the Exchange, and was the 

 place where Prof. Bache had observed. The time was June 10th, 

 1841, Hi A. M. to 1± P. M. The resulting dip 71° 31 '.9, agreeing 

 very well with the determinations of M. Nicollet and Prof. Bache. 



Observations at stations Nos. 3 and 4 were made to ascertain 

 whether a line of iron pipes serving to connect a neighbouring spring- 

 house and dairy, and running nearly E. and W. caused the differ- 

 ences observed in the two stations Nos. 1 and 2. No. 3 was nearly 

 intermediate between Nos. 1 and 2, and 43 feet N. of the line of 

 pipes, bearing of No. 1 for No. 3, N. 35° W. and distance 212 feet. 

 Resulting dip, by two series of observations with one needle, 71° 

 47'. 5. The bearing of No. 3 from No. 4 was N. 8° W. and distance 

 181 feet, and Nos. 3 and 4 were nearly at the same distances N. 



* Proceeding's of the Am. Phil. Society, Vol. I. No. 14. 



