MINERALOGY AND GEOLOGY. io 
ponding to the dip in column A, for each mile of distance. If, therefore, a set of 
strata, dipping at 23°, measure six miles across the strike, the thickness will be 
12378 feet (= 2063 x 6). The third column, Q, gives the thickness in parts of a 
foot for each foot of distance (or in parts of a yard for each yard, etc.); and the 
fourth column, D, shows the depth (in parts of a foot, yard, ete., for each foot, 
yard, or other unit of measurement), at which an inclined bed will be reached by 
vertical sinking at a given distance from its outcrop.{ The figures in these two 
last columns are, of course, nothing more than the sines and tangents respectively 
of the corresponding degrees of dip in column A. 
4 B. C. 2D A. B Cc D A. B Cc. D 
m -|m . eS a 5 n n i = § 5 n n a 2 Ss Q 
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Palaaais8s| Bag al S78 | Bes | Bag 44) S52) S23 | B23 
He; A £2 |A ® i eae een 
1°} 92°15) °0174 | -0174 81°) 2719-4 | +5150 “6008 61°) 4618°0 | °8746 1°804 
2 | 18427) -0349 | 0349 382 | 2798°0 | °5299 “6248 62 | 4661°9 | -8829 1°S880 
8 | 276°33) °0523 | °0524 383 | 2875°7 | °5446 “6494 63 | 4704°5 | +8910 1°962 
4 | 868°32| ‘0697 | -0699 34 | 2952°5 | °5591 °6745 64 | 4745°6 | -S988 2°050 
5 | 460°18] ‘OS71 | ‘0874 35 | 3028°5 | °5735 “7002 65 | 4785°3 | °9063 2°144 
6 | 55191} ‘1045 | +1051 386 | 3103°5 | ‘5877 “7265 66 | 4823°5 | °9135 2°246 
7 | 643°47| °1218 | -1227 37 | 8177°6 | -6018 "7505 67 | 4860°3 | -9205 2° 305 
8 | 734°83) 1591 | °1405 38 | 3250°7 | -6156 *7812 68 | 4895°5 | -9271 2°475 
9 | 825°98} *1564 | -1583 39 | 3322°8 | °6293 “8097 69 | 4929°3 | -9335 2°605 
10 | 916°86| ‘1736 | 1763 40 | 8393°9 | *6427 “8391 70 | 4961'°6 | -9396 Q°747 
11 |1007°5 | °1908 | °1943 41 | 3464°0 | °6560 *§692, 71 | 4992°3 | -9455 2°904 
12 |1097°8 | °2079 | °2125 42 | 8533°0 | *6691 "9004 72 | 5021°6 | -9510 3°077 
13 |1187°7 | °2249 | -2308 43 | 3600°9 | “6820 *9325 73 | 5049°3 | -9563 3°270 
14 |1277°3 | °2419 | °2493 44 | 3667-8 | °6946 *9656 7 5075'5 | *9612 3°487 
15 | 138665 | °2588 | *2679 45 | 8733°5 | *7071 1-000 75 | 5100°1 | -9659 3°782 
16 |1455'3 | °2756 | -2867 46 | 3798°1 | -7193 1°035 76 | 5123°2 | -9703 4°011 
17 | 1543°7 | °2923 | °8057 47 | 38861°5 | °7313 1:072 77 | 5144°7 | -9743 4°331 
18 | 1631'6 | °3090 | *38249 48 | 3923°8 | °7431 17110 78 | 5164°6 | -9781 4°'704 
19 |1719°0 | °3255 | °3443 49 | 3984°9 | +7547 1°150 79 | 5183°0 | -9816 5°144 
20 |1805°9 | °3420 | *3639 50 | 8987°7 | *7660 1°191 80 | 5199°8 | ‘9848 5°671 
21 | 18922 | °3583 | “3883S 51 | 4103°3 | °7771 1°235 8i | 5215°0 | “9876 6'°313 
22 |1977°9 | °3746 | -4040 52 | 4160-7 | *78S80 1-280 82 | 5228°6 | -9902 7°115 
23 | 20630 | ‘8907 | +4244 53 | 4216°8 | °7986 1°327 83 | 5240°6 | -9925 8°144 
24 | 2147°6 | °4067 | °4452 54 | 4271°6 | *8090 1°576 84 | 5251°1 | °9945 9°514 
95 |2231'4 | *4226 | °4663 55 | 4325-1 | °8191 1°428 85 | 5259°9 | -9961 |11°430 
26 | 28146 | °4383 | °4877 56 | 4377°5 | *8290 1°482 86 | 5267°1 | :9975 |14°3800 
27 | 23971 | °4540 | °5095 57 | 4428°2 | °8386 1°539 87 | 5272°8 | -9986 |19°081 
28 | 2478'S | °4694 | °5317 58 | 4477°7 | °8480 1°600 88 | 5276°8 | °9993 |28°636 
29 | 2559'S | "4848 | 5543 59 | 4525°8 | °8571 1°664 89 | 5279°2 | -9998 |57°290 
30 60 | 4572°6 | °S660 1°733 -—-|——_ — 
26400 | :5000 | -5773 
EB. J. C. 
MISCELLANEOUS. 
; NORTH-WEST TERRITORY. 
In the last number of the Journal, (Vol. v. page 545 et seg,) we inserted an 
interesting article from the American Journal of Science and Arts, on the recent 
Canadian expeditions to the North-west Territory. A foot-note in this article, in 
reference to the late astronomer Davip Tompson, reads as follows: 
“Thompson was from 179C, over 80 years in the employ of the Hudson’s Bay 
* This necessarily supposes the surface level to remain unchanged. If the one spot be 
lower or higher than the other, the difference must be deducted from, or added to, the 
depth obtained. 
