294 



which stated that an entire discordance had been found be- 

 tween the curve representing the changes of inclination, on the 

 February magnetic term day, at Toronto, Dublin, Brussels, and 

 Prague, whilst those at the last three named stations agreed 

 very well together. This result, Professor B. stated, confirms 

 the conclusions previously drawn from the observations at 

 short intervals, of Prof. Lloyd and himself, in November last. 



Mr. Walker made some observations in relation to the Ob- 

 servatory of the Harvard University, Cambridge, and stated 

 that extensive arrangements had been made, and were in con- 

 templation, for prosecuting magnetic observations and practical 

 astronomy. 



Professor Bache made a verbal communication of some re- 

 cent determinations of the magnetic dip, made by him at Phi- 

 ladelphia and Baltimore. 



He reminded the Society, that on a former occasion he had submit- 

 ted a comparison of the observations for magnetic dip at various sta- 

 tions, common to the series of Professor Loomis (Am. Philos. Soc. 

 Trans. Vol. VII. N. S.), and to that of Professor Courtenay and 

 himself. The discrepancies at Philadelphia and Baltimore were 

 among the most striking. Having satisfied himself that the dip given 

 by his instrument at the station occupied by Prof. Loomis, near Phi- 

 ladelphia, was sensibly the same as that given by Prof. Loomis, his 

 next step was to ascertain, by observations in a different position from 

 those used in both the sets of observations formerly made, which pro- 

 bably represented more correctly the dip at Philadelphia. The result 

 of two series of observations near the observatory at the Girard Col- 

 lege (at a sufficient distance to be beyond sensible influence from 

 the magnetic instruments), made with four different needles, was as 

 follows : — 



July 21, 1840. No. 1, 71° 51.7'. No. 2, 71° 51.7'. Mean of 

 Lloyd, No. 1 and No. 3, 71° 55.8'. 



November 2, 1840. No. 1, 71° 51.2'. No. 2, 71° 51.0'. Mean 

 of Lloyd, No. 1 and No. 3, 71° 57.4'. 



Mean, 71° 53.3'. 



The needles, termed Lloyd No. 1 and No. 3, are used without re- 

 versing the poles ; and a correction has been applied from the mean 

 of sixteen comparisons, with the ordinary needles, at different places : 

 as, however, this correction is obtained through Nos. 1 and 2, the 



