Velocity and Pressure of the Wind.
The Pressure varies as the Square of the Velocity, or P ∝ V2. The Square of the Velocity in Miles per Hour multiplied by ·500 gives the Pressure in lbs. per square Foot, or V2 × ·005 = P. The Square Root of 200 times the Pressure equals the Velocity, or √(200 × P) = V.
The subjoined Table is calculated from this data, by Col. Sir Henry
James, of the Ordnance Survey Office.
| Pressure in | Velocity in | Pressure in | Velocity in | Pressure in | Velocity in | Pressure in | Velocity in | Pressure in | Velocity in |
| lbs. per | Miles | lbs. per | Miles | lbs. per | Miles | lbs. per | Miles | lbs. per | Miles |
| Square Foot. | per Hour. | Square Foot. | per Hour. | Square Foot. | per Hour. | Square Foot. | per Hour. | Square Foot. | per Hour. |
| oz. | lbs. | lbs. | lbs. | lbs. | |||||
| 0·08 | 1·000 | 6·75 | 36·742 | 17·75 | 59·581 | 28·75 | 75·828 | 39·75 | 89·162 |
| 0·25 | 1·767 | 7·00 | 37·416 | 18·00 | 60·000 | 29·00 | 76·157 | 40·00 | 89·442 |
| 0·50 | 2·500 | 7·25 | 38·078 | 18·25 | 60·415 | 29·25 | 76·485 | 40·25 | 89·721 |
| 0·75 | 3·061 | 7·50 | 38·729 | 18·50 | 60·827 | 29·50 | 76·811 | 40·50 | 90·000 |
| 1·00 | 3·535 | 7·75 | 39·370 | 18·75 | 61·237 | 29·75 | 77·136 | 40·75 | 90·277 |
| 2·00 | 5·000 | 8·00 | 40·000 | 19·00 | 61·644 | 30·00 | 77·459 | 41·00 | 90·553 |
| 3·00 | 6·123 | 8·25 | 40·620 | 19·25 | 62·048 | 30·25 | 77·781 | 41·25 | 90·829 |
| 4·00 | 7·071 | 8·50 | 41·231 | 19·50 | 62·449 | 30·50 | 78·102 | 41·50 | 91·104 |
| 5·00 | 7·905 | 8·75 | 41·833 | 19·75 | 62·819 | 30·75 | 78·421 | 41·75 | 91·378 |
| 6·00 | 8·660 | 9·00 | 42·426 | 20·00 | 63·245 | 31·00 | 78·740 | 42·00 | 91·651 |
| 7·00 | 9·354 | 9·25 | 43·011 | 20·25 | 63·639 | 31·25 | 79·056 | 42·25 | 91·923 |
| 8·00 | 10·000 | 9·50 | 43·588 | 20·50 | 64·031 | 31·50 | 79·372 | 42·50 | 92·195 |
| 9·00 | 10·606 | 9·75 | 44·158 | 20·75 | 64·420 | 31·75 | 79·686 | 42·75 | 92·466 |
| 10·00 | 11·180 | 10·00 | 44·721 | 21·00 | 64·807 | 32·00 | 80·000 | 43·00 | 92·736 |
| 11·00 | 11·726 | 10·25 | 45·276 | 21·25 | 65·192 | 32·25 | 80·311 | 43·25 | 93·005 |
| 12·00 | 12·247 | 10·50 | 45·825 | 21·50 | 65·574 | 32·50 | 80·622 | 43·50 | 93·273 |
| 13·00 | 12·747 | 10·75 | 46·368 | 21·75 | 65·954 | 32·75 | 80·932 | 43·75 | 93·541 |
| 14·00 | 13·228 | 11·00 | 46·904 | 22·00 | 66·332 | 33·00 | 81·240 | 44·00 | 93·808 |
| 15·00 | 13·693 | 11·25 | 47·434 | 22·25 | 66·708 | 33·25 | 81·547 | 44·25 | 94·074 |
| 11·50 | 47·958 | 22·50 | 67·082 | 33·50 | 81·853 | 44·50 | 94·339 | ||
| lbs. | 11·75 | 48·476 | 22·75 | 67·453 | 33·75 | 82·158 | 44·75 | 94·604 | |
| 1·00 | 14·142 | 12·00 | 48·989 | 23·00 | 67·823 | 34·00 | 82·462 | 45·00 | 94·868 |
| 1·25 | 15·811 | 12·25 | 49·497 | 23·25 | 68·190 | 34·25 | 82·764 | 45·26 | 95·393 |
| 1·50 | 17·320 | 12·50 | 50·000 | 23·50 | 68·556 | 34·50 | 83·066 | 45·50 | 95·131 |
| 1·75 | 18·708 | 12·75 | 50·497 | 23·75 | 68·920 | 34·75 | 83·366 | 45·75 | 95·655 |
| 2·00 | 20·000 | 13·00 | 50·990 | 24·00 | 69·282 | 35·00 | 83·666 | 46·00 | 95·916 |
| 2·25 | 21·213 | 13·25 | 51·478 | 24·25 | 69·641 | 35·25 | 83·964 | 46·25 | 96·176 |
| 2·50 | 22·360 | 13·50 | 51·961 | 24·50 | 70·000 | 35·50 | 84·261 | 46·50 | 96·436 |
| 2·75 | 23·452 | 13·75 | 52·440 | 24·75 | 70·356 | 35·75 | 84·567 | 46·75 | 96·695 |
| 3·00 | 24·494 | 14·00 | 52·915 | 25·00 | 70·710 | 36·00 | 84·852 | 47·00 | 96·953 |
| 3·25 | 25·495 | 14·25 | 53·385 | 25·25 | 71·063 | 36·25 | 85 146 | 47·25 | 97·211 |
| 3·50 | 26·457 | 14·50 | 53·851 | 25·50 | 71·414 | 36·50 | 85·440 | 47·50 | 97·467 |
| 3·75 | 27·386 | 14·75 | 54·313 | 25·75 | 71·763 | 36·75 | 85·732 | 47·75 | 97·724 |
| 4·00 | 28·284 | 15·00 | 54·772 | 26·00 | 72·111 | 37·00 | 86·023 | 48·00 | 97·979 |
| 4·25 | 29·154 | 15·25 | 55·226 | 26·25 | 72·456 | 37·25 | 86·313 | 48·25 | 98·234 |
| 4·50 | 30·000 | 15·50 | 55·677 | 26·50 | 72·801 | 37·50 | 86·602 | 48·50 | 98·488 |
| 4·75 | 30·822 | 15·75 | 56·124 | 26·75 | 73 143 | 37·75 | 86·890 | 48·75 | 98·742 |
| 5·00 | 31·622 | 16·00 | 56·568 | 27·00 | 73·484 | 38·00 | 87·177 | 49·00 | 98·994 |
| 5·25 | 32·403 | 16·25 | 57·008 | 27·25 | 73·824 | 38·25 | 87·464 | 49·25 | 99·247 |
| 5·50 | 33·166 | 16·50 | 57·415 | 27·50 | 74·161 | 38·50 | 87·749 | 49·50 | 99·498 |
| 5·75 | 33·911 | 16·75 | 57·879 | 27·75 | 74·498 | 38·75 | 88·034 | 49·75 | 99·749 |
| 6·00 | 34·641 | 17·00 | 58·309 | 28·00 | 74·833 | 39·00 | 88·317 | 50·00 | 100·000 |
| 6·25 | 35·355 | 17·25 | 58·736 | 28·25 | 75·166 | 39·25 | 88·600 | ||
| 6·50 | 36·055 | 17·50 | 59·160 | 28·50 | 75·498 | 39·50 | 88·881 |
This is the only table hitherto much in use for converting velocity into pressure, and was prepared by Smeaton and others. It does not, however, express the true relation, which has yet to be determined.
The Anemograph, or Self-Recording Wind Gauge, has for its object the registration of the velocity and direction of the wind from day to day. Figs. 59 and 60 show the form designed and arranged by Mr. Beckley, of the Kew Observatory, which has been adopted by the Meteorological Office.
59.
Anemograph. Scale about 1/20.
Portion for exterior of observatory.
It consists of a set of hemispherical cups and vanes, which are exposed on the roof of the house, and of the recording apparatus, which is placed inside the house.