AND THE INTENSITY OF MAGNETICAL FORCE, oll 
V. SERIES, 1842, CINCINNATI TO CAMBRIDGE, (MASSACHUS Bote 
PEPE a Horizontal |'Total Intensity, | rtal x Total: Intensity 
No. Date. Place. Latitude. Longitude, Dip. Intensity.| Hor. being 1000. | tte alge bbe Sabine’s unit. 
67iMarch 81,/Cincinnati, « = . « 39° 06’ | 84° 22’ 70°20'20"|1000.54| 2973.72 | 996.19 
58/My.8,'41,/Cincinnati, - - - - 39 06 | 84 22 /70 2611 |1000, 2986.38 (1000. 
59Ap.7,742,|/Pittsburgh, = - « = 40 32 | 80 02 /72 4312] 890.738) 2998.64 |1004.10 
60). April 9, |Chambersburg, - * 39 65 177 +40 171 67 04) 921.57)" “2075.52 996.36) 
61) “ 12,)Mt. St. Mary’s Coll lege, | 39 41 |'77 18 |71 4620) 931.90) 2997.26 | 997.66) 
62| « 21,,New Haven, - - - |41 18 | 72 56 (73 2947 | 838.54) 2951.82 | 995.18) 
63| May 2, |Boston, - - - = = |42 22 |70 59 |74.0540| 805.72) 2940.02 | 984.47 
64, “ 4, |\Cambridge, - = ~ = 741452} 804.02; 2961.64 | 991.71 
65). “ »18,)Bristol, + = «04.4 40 06 | 74 47 172 25 888.45} 2941.56 | 984.99 
66) “ 15,/Philadelphia, - - « 72 OL 917.85) 2972.88 | 995.48) 
VI. SERTES OF 1843, LAKE SUPERIOR, &e. 
67; Aug. 21,Cincinnati, - - = - | 89° 06" | 84° 22’ "/70°25'30")1000.76] 2986.98 |1000.20* | 
68}  21,jCincinnati, - - - »« 39 06 84 22 70 25 30 |1000. 2986.98 |1000. | 
69] June 6, |Hudson, Ohio, - - - | 41 26 | 82 27 (73 0000 | 883.40} 3021.50 (1012.32 | 
70 “ 12,)Detroit, Michigan, = = 42 25 82 56 (7 73 32 855.63} 3018.55 LOLL.34) | 
re « 13,Ann Arbor, - - = « 42 16 | 8339W.'73 12 36 | 877.86} 8039.00 |1018.20 | 
72 paca i jAnn Arbor, = = - = 42 16 | 83 89 |73 1446] 876.48} 3030.40 [1018.64 | 
73 " 15, (Detroit, = - -@. - 42 25 82 56 (73 8225 | 854.89) 3017.17 |1010.90 ' 
74, +“ 18,/Mackinaw, - - - + 45 54 | 84 10 /76 38 51 | 715.87) 3100.40 {1038.75 | 
75 Sanlt St. Marie, - - 46 31 84 32 (77 3015 | 669.47) 3094.10 |1036.65 | 
76) July 2, | ncampment, L.Superior, 46 44 | 87 43 |76 5819 | 695.91) 3087.10 (1034.10 
77| « 8, |/Houghton’s River,- - | 4728 N.) 88 O1 77 2045 | 671.24] 3064.30 |1026.62 | 
78| +‘ 8, [Magnet Inlet, .« « - 47 283 | 88 01W./78 45 20 | 619.14, 3175.00 1063. 80 
79| & J1,JMagnet Inlet, « « » 66 66 78 43 20 | 620.80} 8183.62 /1066.66 | 
80 « 15,500 ft. east of Mag. Inlet, 66 st 78 37 30 ie 623.59} 3160.70 |1059.31 | 
81 “ 1,jisthmus, -  - - & 88 00 |78 28 | 629.88} 8150.38 11055.50 | 
82; * 8, [United States Apene vs 6 “ 77:13 30) 717.18] 3243.20 |1086.58] 1.97029 | 
g3} « 13,Eagle River, - - = | 47 27 [88 28 (77 54 oo 648.20| 3094.40 |1036.72 | 
84, “ 21,/La Pointe, - - - - |46 47 |90 58 1/76 56 704.72} 3117.5 1044.50) 1.89400 
85|  26,/Ontonagon, - - - - |46 52 | 89 31 771310 | 686.17] 3101.81 |1039.23 | 
86} oe Isle Royale,- - - - |48 06 |88 47 |78 0736 | 646.40] 3141.7 [1052.60] 1.90808 | 
87) Au Aug. 4 {C le svels and, Ohio, - - 7s 3 08 | 880.17 3033.54 [1016.34 | 
* The above quantities refer to “Cincinnati, May 8, 1841,’ as unity. In the following series the standard, 
assumed is that of Cincinnati, August 21, as unity, both of horizontal and total intensity, as follows. 
GEOLOGY OF PORTER’S ISLAND AND COPPER HARBOUR. 
The geology of this and the neighbouring regions, has been well treated by Dr. Hough- 
ton, the geologist of the state of Michigan, to whose writings we refer the reader for 
information more general than it is my object, in this article, to present. The rocks of 
Copper Harbour, and indeed of the whole of Kewenon peninsula, are decidedly meta- 
morphic, showing every degree of change produced by igneous agency, from unchanged 
sandstone to compact greenstone. ‘The original stratification is, mostly, more or less 
evident, presenting in the various superimposed layers, an inexplicable variety, some 
layers bearing evidence of semi-fusion and a correspondent degree of induration and endu- 
rance, while others seem scarcely to have been altered, still remaining soft and yielding 
readily to atmospheric agency, and especially to the assaults of the waves from the lake. 
Whether these differences have been produced by an unequal distribution of the heat, or 
by an original difference in the layers of the strata, some being of a nature more Suscep- 
VOL. IX.—82 
