TERRESTRIAL MAGNETISM. 



27 



Dip. 



^ 1 



Epoch of 

 dommencing 

 vibration, 

 hrs. min. sec. 



Duration 

 of 500 

 vibra- 

 tions. 



as 



B 2 



Calculated 



duration 



at 60°. 



Square of the 

 preceding. 



Horizon- 

 tal inten- 

 sity. 



Total in- 

 tensity : 

 hor. being 

 1000. 



Total inten- 

 sity : that at 

 Cincinnati 

 = 1000. 



221. Island five or six miles north of Mackinaw (St. Martin's Island?).— Lsit. 45° 59' 



N. Long. 84° 47' W. August 28, 1847. 



76° 43' 30" 



4 

 5 

 6 



8 18 02.4 1318.88 



3 42 24.0 P 1599.61 



4 05 05.0 P 1590.82 



66 

 66 

 64 



1318.34 

 1598.94 

 1590.25 



17380203556 



25566091236 



25289268676 



Mean 



712.74 

 713.68 

 713.26 

 713.22 



3106.0 



1038.1 



222. Twenty-five miles west of Mackinaw, on the lake shore. — Lat. 46° 03' N. Long. 

 85° 21' W. September 3, 1847. 



76° 55' 31" 



5 



1 40 04.0 



2 02 01.6 



1609.6 

 1602.6 



67 

 66 



1608.81 25882374400 



1601.75 25656030625 



Mean 



704.96 

 702.67 

 703.82 



3111.1 



1039.8 



223. Mouth of Seul Choix River.— Lat. 45° 59' N. Long. 86° 08' W. September 6, 1847. 



76° 35' 15" 



5 



9 38 04 A 



1589.62 



67 



1588.74 25240947876 722.87 1041.3 





224. Seven miles west of Seul Choix Point.— Lat. 45° 58' N. Long. 86° 15' W. Sep- 

 tember 8, 1847. 



76° 25' 37" 



5 

 6 



12 42 44.0 

 12 57 59.2 



1590.62 

 1581.62 



60 

 60 



1590.62 

 1581.62 



25300719844 



25005096900 



Mean 



721.17 



720.82 

 720.99 3071.8 



1026.6 



225. Ministique River.- Lat. 45° 58' N. Long. 86° 29' W. September 9, 1847. 



76° 24' 09" 



4 

 5 

 6 



6 16 04 P 

 5 49 05 

 5 31 00 



1303.70 

 1581.62 

 1574.62 



60 

 60 

 61 



1303.70 

 1.581.62 

 1574.50 



16997336900 



2501.5218244 



24790502500 



Mean 



728.79 

 729.40 

 727.21 



728.47 



3098.0 



1035.4 



226. Moon Island.— Lat. 45° 36' N. Long. 87° 17' W. September 11, 1847. 



76° 18' 40" 



5 

 6 



11 31 08.0 A 

 11 59 01.6 



1580.62 

 1574.62 



64.0 

 65.5 



1580.22 

 1574.02 



24964000000 



24774760000 



Mean 



730.70 

 727.60 

 729.15 



3080.5 



1029.6 



REMARKS. 



221. Island five or six miles north of Mackinaw. (St. Martin's Island?) — Range 2 W., township 

 41 N., section 9. Geology : cliff limestone, horizontally stratified. 



222. Twenty-five miles west of Mackinaw. — Range 7 W., township 42 N., section 12; United States 

 surveys. Geology: sand, superimposed on cliff limestone. 



223. Mouth of Seul Choix River. — Range 13, township 40, section 11. Geology : cliff limestone. 



224. Seven miles west of Seul Choix Point. — Range 14, township 41, section 10. Geology: sand, 

 superimposed on cliff limestone. 



225. Ministique River. — Range 26 W., township 41, section 18. Geology : sand, superimposed on 

 cliff limestone. 



226. Moon Island.— Geology : sand, superimposed on cliff limestone. 



