1815.] -the Rise and Fall of the Tide. 277 
with instruments for measuring the force and velocity of the wind, 
the following remarks, the result of many observations, may serve 
as a guide to judge of the rate at which the wind is blowing. 
When the wind blows at the rate of 12 geographical miles per 
hour, or 20°29 feet in a second, the power of the wind on a plane 
one foot square at right angles to the current is equal to 13°567 oz. 
avoirdupois ; and the generality of vessels upon a wind blowing at 
this rate can barely carry top-gallant sails. 
When the wind blows 24 geographical miles per hour, the force is 
3°54] lbs, avoirdupois, and vessels are under close reefed topsails. 
When the wind increases to 31°16 geographical miles in an hour, 
vessels are under their courses, and the power of the wind is equal 
to.6 lbs. 
When the force of the wind is 8 Ibs. on a square foot, its velocity 
is 35°931 geographical miles in an hour, and may be denominated 
half a storm. 
When the strength of the wind is 12 lbs. on a square foot, its 
velocity is 43918 geographical miles in an hour, and may be called 
a full storm. : 
‘Whilst on this subject, I have subjoined some experiments on the 
resistance of air and water, which prove how very erroneous the 
theory of resistance is, and the small advantage it has been to prac- 
tical men. 
Experimented Resistance of Air to different shaped Bodies. 
“ 
Feet. | Plane, | Cylinder.) Cone. | Vertex. Wedge, | Vertex, 
1 0-032 0'028 0-029 0 020 0:022 0:032 0:023 
2 0-129 0-116 07120 0:086 0:090 0°129 0-089 
3 0-294 0-268 0'2T4 0'198 0203 0:291 0°197 
4 0°525 0-485 0°492 0°358 0°364 0-518 0°346 
aoe 0°825 0-768 0175 0°567 0-571 0'810 —0°53T 
6 1191 1-118 1-122 0-826 0°825 1168 0:769 
a | 1627 1537 1 535 1°135 1}27 1-490 1-041 
8 2131 2-024 2°013 1-494 1476 2-070 1°354 
9 2-704 2-580 2°564 1:905 | 1873 2°634 1°T07 
10 3°345 3°206 3: 167 2°268 2317 3°253 2°100 
| 4°055 3°902 3°843 3017 2 809 3°939 2-533 
12 4834 4-668 4°586 8°610 8°348 4-690 3°005 
13 5683 5°505 5°395 4-066 3°936 5506 3°518 
14 6-601 6-413 6271 AT3T 4°572 6°389 4-069 
15 7'588 7°393 7T°231 5462 5255 T3387 4661 
16 8644 8445 §°295 6239 5 9388 $351 5:292 
sr ag 9-771 9°570 9°302 7-068 6167 9-430 5-961 
18 | 10-966 | 10-767 | 10-447 | 7-952 | 7-595 | 10576 | 6-670 
19 | 12-232 | 19-038 | 11-660 | #890 | 8-479 | 1ie787 | 7-419 
20 | 13567 | 13-378 | 19-940 | 9-882 | 9-397 | 13-064 | 8-207 
7“———— |) ————_—— _ ee oo a 
p | 20201 | 20611 20309 | 2:0619 2:0057 | 1-9 676 
ne eg Ss et ee | 
} 2 3 4 5 
6 7 8 
The area of the plane and base of each of the bodies is exactly 
one superficial foot ; and the altitude of the cylinder, cone, and 
wedge, equal to half the diameter of their respective bases ; conse- 
