AND THE INTENSITY OF MAGNETICAL FORCE. 305 
69. Mackinaw Island, Latitude 45° oni N.; Longitude 84° 10’, W.; June 18, 1843. 
et ‘ "| Duration "| Calculated : To! 
Dip. No.of {Epoch of commencing] of 500 |Tempe-| duration Square of the Horizontal | Total intensity, |that 2 
Needle. Vibrations, Vibrations | rature, at 60°, preceding. intensity. |Hor. being 1000. [nati being 1000. 
reomvemasan | coms 
| . 
76°38/51") 4 | 9h.18m.088.6 A}1812.0 /71°5 |1310.8 |1718196.6400) 716.47 
5 |10 00 04 8 {1599.6 |75 0 |159'7.66|2552517.4756) 715.23 
6 |10 49 00 0 {1593.2 |79 0 |1590.28)2528990. Pig oh 
Mean,| 715.87 3100.4 1088.75 
About three hundred yards west of the highest point of the island. Geology, the cliff 
limestone, very much disturbed and broken. Clear, calm, beautiful. Some calm cirri. 
70. Sault de St. Marie, Latitude 46° 31’, N.; Longitude, 84° 32’, W. 
77°30'15"| 4 |11h.65m.02s, Eisner | 86° |1357.08|1841666.7264|668.43 | 
5 |12 29 06 PI1655.2 | 89 |1651.57|2727683.4649 669.29 
6 | 1 05 06 1647.6 | 90 |1643.00/2699449.0000/670.69 
| | Mean,|669.47 | 3094.10 | 1036.65 
About four hundred yards west of the mill-race, and near the proposed canal around 
the Sault. Geology, diluvium, superimposed on horizontally stratified sandstone. 
71. Encampment about ten miles below St. John’s River, Lake Superior; Latitude 46° 44’, N.; Longitude 
87° 43’, W.; July 2, 1848, 
76°58'19"| 4 8h.06m.04s. A|1330. 60° |1768314,8484 696.16 
5 8 59 00 1620. 60 = |1619.73/2623525.2729 695.87 
6 9 35 08 1613.6 | 61 |1613,.2 /2602414.2400 695.70 | 
Mean, 695.91 3087.10 | 1034.10 
| 
| 
In a swamp of cedar, fir, and white birch trees, underlaid by horizontally stratified 
sandstone, but with trappean rocks not far distant both ways on the lake shore. 
At this locality, a small island, distant about three miles, bears north 69° east, and, 
another, distant half of a mile, bears north 7° west. ‘The last is so near the shore as to 
leave a channel not more than one hundred and twenty yards wide. A small rivulet puts 
in between our encampment and the point opposite this island. Clear, wind north-west, 
strong. 
72. Houghton’s River, near Copper Harbour, Latitude 47° 28’, N.; Longitude 88° 01’, W.; 5 duly 8, 1843. 
77°20'45"| 4 12h,38m.028.4 P|1356.0 (71°5 |1854.77|/1835401.752 29/670. 71 7 
5 1 15 O01 6 {1650.8 {72 ; 1648.35/2717657.7225/671.91 
6 2 00 04 8 {1644.4 /72 0 |1642.4 /2697477.7600/671.18 | 
Mean,|671.27 3064.30 | 1026.62 
t 
This locality is designated on the map bya circlet and the letter @. Substratum, 
metamorphic conglomerate, approaching, apparently, to trap rock in its nature. Clear, 
wind north-west. 
73. Magnet Inlet, Porter’s Island, Copper Harbour, Latitude 4'7° 29’ N,; Sey tre 88° 02’ W,; Per © 8, alte 
"78°45'20" 4 |11h.48m. 025.4 Al1411.2 | 62° |1410. 8 |19903 356. 64 |618.50 
0.212 “flo 00s ea PIG b CO 171% 32,2949187,9824 619.03 
6 1 10 04 8 /|1709.6 | 58 Shine parte 1.0000)619.89 
Mean,|/619.14 | 3175.10 1063.80 
This station is designated, on the map of Porter’s Island, as station No.7. Wind 
north-west, strong. 
Sag ee 
in 
