WEATHER NOTATION.
The following letters are used to denote the state of the weather:—
| b | denotes | blue sky, whether with clear or slightly hazy atmosphere. |
| c | „ | cloudy, that is detached opening clouds. |
| d | „ | drizzling rain. |
| f | „ | fog. |
| h | „ | hail. |
| l | „ | lightning. |
| m | „ | misty, or hazy so as to interrupt the view. |
| o | „ | overcast, gloomy, dull. |
| p | „ | passing showers. |
| q | „ | squally. |
| r | „ | rain. |
| s | „ | snow. |
| t | „ | thunder. |
| u | „ | ugly, threatening appearance of sky. |
| v | „ | unusual visibility of distant objects. |
| w | „ | wet, that is dew. |
A letter repeated denotes much, as rr, heavy rain; ff, dense fog; and a figure attached denotes duration in hours, as 14r, 14 hours’ rain.
By the combination of these letters all the ordinary phenomena of the weather may be recorded with certainty and brevity.
Examples.—bc, blue sky with less proportion of cloud; cb, more cloudy than clear; 2rrllt, heavy rain for two hours, with much lightning, and some thunder.
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.
The motion imparted to the hemispherical cups by the wind is communicated to the steel shaft B, which, passing through the hollow shaft C, and having at its lower end an endless screw, works into a series of wheels in the iron box D, which reduces the angular velocity 7,000 times. At the required distance the motion, having emerged at E, is connected with F, where, by means of bevelled wheels, it moves the spiral brass registering pencil C, which is arranged so that each revolution records 50 miles of velocity on the prepared paper H.
The direction of the wind is indicated by the arrow L, which is kept in position by the fans M. These communicate, by an endless screw and train of wheels, through the shaft C and the box D to the recording apparatus, consisting of a spiral brass pencil, which in one revolution records variations through the cardinal points of the compass, on the same prepared paper as that which receives the record of velocity.
60.
Anemograph. Scale about 1/20.
Portion for interior of observatory.
The paper is held on the drum by two small clips, and may be readily changed, by unclamping the cross V, without disturbing the drum or any other part of the instrument.
61.
Self-recording Magnetometer, Kew Observatory.