306 OBSERVATIONS ON THE MAGNETIC DIP, 
74. Magnet Inlet, July 11, 1848. 
Duration Calculated} Total intensity, 
Dip. No. of S geese ofcommencing} of 500 |Tempe-| duration Square of the Horizontal|Total intensity, |that at Cincin- 
Needle, Vibrations. Vibrations. /rature. at 60°. preceding. intensity.| Hor. being 1000. /nati being 1000. 
a | 
78°45'20” 6h.28m.04s. P)1408.4 | 66° |1407. 621981394, 0644 |621,29 
4 
5 | 6 54 00 1716.0 | 61 5,1715.54,2943077.4916 |620.31 
6 |Not used. | Mean, |620.80 | 3183.62 | 1066.66 
The geology, &c., of this locality will be discussed after we shall have presented all 
of the observations made about Copper Harbour. 
75. Five hundred feet east of Magnet Inlet, July 15, 1843. 
.2500/624,06 
2926733.9929|623.77 
29064.11.2324/622.93 
Mean,|623.59 3160.70 1059.81 
-78°37'30" 
4 | 4h.3%m.00s. Pj1406. | 74° [1404.5 
5 |5 00 04 4 \1712, | 68 |1710.775 
| 6 | 5 82 01 6 1706. | 66 /1704.82 
} 
In a grove of small spruce and fir trees. “ Station 8, on map of Porter’s Island. 
76. On the Isthmus between the lower end of Copper Harbour and the “ White rock,” July 11, 1848; 
Latitude 47° 29’, N.; Longitude 88° 00’, W. 
78° 28' | 4 [10h.48m.003, .A/1399.6 | 71° 1398.37|1955438.6569|629.54 
s 11 22 04 4 |1704.0 | 72 1703.30 2901230.8900 629.26 
6 
i 
112 01 04 0 |1696.0 
71 = |1694.08/2869907.0464/630.86 
| Mean,|629.88 3150.88 | 1055.50 
Substratum, metamorphic conglomerate. The experiments were made in the shadow 
of the trunk of a dead tree. 
77. Near General Cunningham’s Office, and eleven hundred feet westwardly of Magnet Inlet, on Porter’s Island, 
July 8, 1843. Station No. 3. 
77°13'380"| 4 6h.53m.008.8 P|1309.6 | 58° 1309.56 1714947. 3936)/717.82 
5 | %, 238 08-'6 11596, 55 |1596.3 |2548173.69 |716.44 
6 Mean,|717.13 3243.20 1086.58 
It appears from the preceding that there are great variations of the magnetic elements 
on, and about, Porter’s Island, within very small distances. The mean of the total 
intensity at five different stations, about Copper Harbour, will be 3158.90, as follows: 
1. At Houghton’s River, . : : ; : é ‘ ‘ 3064.30 
2. At Magnet Inlet, ‘ > ‘ ‘ ‘ ; 3175.10 
3. Five hundred feet east of Magnet Inlet, ‘ ; : : ‘ 3160.70 
4. Isthmus of the White Rock, ; ; : i j * 7 3151.00 
5. Near the he ed Office, . i 4 F j i j j 3243.20 
Mean, . : : ; i . ; ; . 3158.90 
Assuming the above mean as the total intensity at (Copper Harbour) Magnet Inlet, 
we have by the horizontal intensity given above, “619.14,” and, by the application of the 
formule already given, the calculated dip 78° 41’ 49”, within 3’ 31” of the observed dip 
at the same locality. ‘Thus the unusual dip at this place is proved by two sets of direct 
observations, and by the vibrations of three intensity needles, also twice repeated. 
In order to examine, more in detail, the changes of the dip in various parts of the 
island, I selected that needle, (No. 2,) and the sande of using it, which gave, at a single 
