OBSERVATIONS ON THE MAGNETIC DIP AND DECLINATION. 347 
and 5th of June, 1841, and those made at the observatory of the Girard college, Philadel- 
phia, on the 14th of the same month, are given in full detail. AJl the other observations 
are reported in an abbreviated form. 
It is proper to remark, that, at all the stations embraced by this paper, the several 
readings of the two needles were quite as consistent as those reported at full length. 
The latitude and longitude of every station are given. With the exception of the 
stations at Washington, Baltimore, Philadelphia, New York, Boston, Cambridge Mas- 
sachusetts, and Portsmouth New Hampshire, these have been exclusively derived from 
numerous astronomical observations made by the author of this paper. 
The precise locality of each station, with respect to conspicuous surrounding objects, 
is also given, to enable future observers to place their instruments upon the same points, 
in order to a fair comparison of results, and for a more satisfactory deduction of the 
periodical variation of the dip. 
Although the instrument has been transported over about four thousand miles in the 
various journeys made with it, sometimes in rail-cars, sometimes in stage-coaches, some- 
times in baggage wagons, over exceedingly rough roads, and sometimes in log and bark 
canoes, while navigating shoal rivers, abounding with rocks and dangerous rapids, yet 
it is uninjured in the slightest degree. The last observations made with it are quite as 
satisfactory as any of the series. This is to be attributed to the admirable manner in 
which the instrument is packed in its travelling-case, and the attention that was always 
bestowed to ensure its safety. 
The temperature is always given by the scale of Fahrenheit. 
The longitudes are always given west of Greenwich. 
The time of observation given is always mean solar time, by civil reckoning. 
XII. OBSERVATIONS FOR THE DIP OF THE MAGNETIC NEEDLE, WITH INSTRUMENT BY GAMBEY, 
OF PARIS. 
Date and place of observation —1841, June 1st.—Washington City, D.C. In the centre 
of the public garden, east of the capitol. Latitude 38° 53’ 30”, N.; Longitude 
77> O17-80"%, W. 
Solarlty.c i sdside| Mean solartime/North end of Needle/South end of Needle | Mean of both ends ache ‘ 
Noval. i lt fubservation.| reads | ___reads | of Needic. __frnermometer| “or? 
of Needle. H. M. Deg.|Mins.grenths,|/Deg.| Mins &Venths, | Deg.| Mins.§Tenths. | (Fahrenheit.) | Observer. 
1 N E E 8.16a.M.) 71 . 15 at 18 71. 16.5 76° 
6 6 ‘6 “ 8.20 we. Le Ti-« 18 71.16 
“ 6“ 6 “ 8.24 71.43 71.16 712 18.5 
6 66 6 “ 8.30 y ie | 71.5 15 71 13 * 
“ «“ Ww w | 8.40 71. 00 70 . 56 70 . 58 78 a 
« « «“ «“ 8.45 70. 57 70 . 52 70. 54.5 a 
« «“ «“ «“ 8.50 70 . 58.5 70. 54 70 . 56.2 78 & 
“ “ & 8.55 70. 59 70.55 70... 57 ‘ 
«“ «“ WwW E 9.10 71, 35 Zi. 29 71. 32 79 A 
‘“ «“ «“ “ 9.12 71. 35 W127 71281 80 er) 
6 6 6c 6“ 9.18 V1. 86 TL 29 T1382 & 
“ “ “ “ 9.20 71. 85 F128 71 531.5 81 = 
“ “ E WwW 9.33 70. 42.5 70. 49 70. 45.7 82 Re 
66 “ 6c “ 9.35 70. 44 70, 50 70.47 
6 “ “ 66 9.37 70. 48 70.49 70. 46 Be 
“ + “ “ 9.40 70.43 70.48 70 45.5 84 
VoL. IX.—91 
