8 Molesworth’s pocket-book .
Dip of Horizon;
D = Pip of horizon in seconds.
H = Height of observer’s eye in feet.
S = Distance of horizon in statute miles.
N = Do. do. nautical miles.
D — 57 • 4 V H. Approximate, varying with
temperature.
H=-663 N2. = -498 S2._
S = 1’42V11. N=1-23VH.
Table of Dip and Distance of Horizon at
Various Heights.
H. S. N. Dip. 1 S- _ N. Dip.
» W I II
5 3'16 2'15 2 8 80 12-67 11 8 33
10 4’48 3’89 3 1 90 13-44 11-66 9 4
15 5-49 4-76 3 42 100 14-14 12-3 9 34
20 6-34 5-5 4 16 ' 150 17-35 15-06 11 43
25 7-10 6-15 4 47 200 20-04 17'4 13 32
30 7-76 6-73 5 14 300 24-54 21-3 16 34
35 8*38 7-27 5 39 400 28-34 24'6 19 8
40 8'98 7-78 6 3 500 31'62 27-5 21 23
45 9*51 8-25 6 25 1000 44-72 38'89 30 14
50 10-02 8-7 6 46 52000 63’37 55 42 47
60 10-97 9-52 7 24 53000 77-61 67-4 52 24
70 11-83 10'28 8 0 ’4000 89'68 77’8 60 33
Marine Surveying.
To determine the posi-
tion of any sounding A
when afloat take simulta-
neously the bearingflf three
known objects on shore,
BCD, plot the angles on
tracing paper, and move
them on plan until the
linea cut the points B C I>.