Plan for a Meteorological Journal. 231 



Art. III. Plan for a Meteorological Journal, to he Icept at different 

 Places, with a Vietv to the Anticipation of " coming Weather." By 

 Mr. GoRKiE, F.H.S. &c. 



Sir, 

 I HAVE been favoured with yours of the 1 1th and 12th, enclosing a 

 copy of a letter to you from Mr. Rogers, Southampton, respecting hints, 

 by Mr. John Machray, as to " coming weather " (p. 109.) ; and I have 

 much pleasure in complying with your request, and offering a mode to be 

 by you submitted to the consideration of Messrs. Rogers and Machray ; 

 or, if you think proper, to be printed in the next Number of the Magazine 

 as an introductory essay on the subject. 



My ingenious young friend, Mr. John Machray, seems to inherit a little 

 of that trait of character pecuhar to us who claim kindred with the second- 

 sighted " C/ait-nan-Gae/," firmly believing that " coming events cast their 

 shadows before." It is a popular opinion that storms generally come upon 

 us from the south, " whence comes good but rare : " the result of our 

 observations, if regularly published in your widely circula^.ed Magazine, 

 will show how far that opinion is entitled to credit ; to do the subject jus- 

 tice, however, it is necessary that our observations be taken in a uniform 

 manner, and on definite and scientific principles. To give an account of the 

 weather of every day, from three places, would, I apprehend, be extremely 

 fatiguing to your readers, in whatever form that account appeared ; and 

 unless " storms," which seem to be Mr. Machray's leading object, occupy 

 a prominent part, the result he wishes to ascertain might be overlooked. 



As wind forms a prominent agent in storms, its direction and velocity 

 ought to be strictly remarked. Mr. Rogers will agree with me, that the 

 terms "wind moderate," "wind very high," or " wind lulled to rest," are too 

 indefinite to enable us to arrive at any practical result. A very simple and 

 at the same time philosophical anemometer, invented by Professor Leslie *, 

 and which is easily within our reach, will enable us to hold a common and 

 intelligible sort of language on that subject. 



The professor found that " the cooling power of a stream of air is pro- 

 portional to its velocity ; " and, from an algebraic formula, we have the 

 following simple rule : — Mark the temperature indicated by a thermometer 

 in the still air ; apply the hand to the ball till the alcohol rises a certain 

 number of degrees ; then mark the number of seconds that elapse till it 

 fall exactly half the number of degrees raised. Raise the alcohol again the 

 same number of degrees, and expose the ball to the full impression of the 

 wind, and mark the number of seconds that it takes to fall half the number 

 of degrees it rose. Divide the number of seconds elapsed in still air by the 

 number of seconds elapsed in \\\e full play of the ivind, throw off 1 from the 

 quotient, and multiply it by \\ : the product expresses the velocity of the 

 wind in miles per hour. For example : suppose the temperature in the still 

 air is 50°, and that it is raised by the hand to 70°, and that it requires 

 100 seconds to cool down to 60", or the half of the increase to which it 

 was raised; suppose that it is exposed to the current of the wind, and is 

 raised to the same height, and cools down to 60° in 10 seconds, the example 

 will stand thus: — Divide 100 by 10, which gives 10; throw off 1, and 

 multiply 9 (tlie remainder) by 4i, which will give 40^ miles per hour. ( See 

 Brewster's Encyclopccdia, art. Anemometer.) I may here remark, that, at 

 the sluggish motion of 1 mile per hour, the dii'ection of the wind is hardly 

 perceptible; at 5, it is a gentle wind; at 11 miles per hour it is called a 

 pleasant brisk gale; at 3o, a high wind; at 50, very high wind; at 62, a 

 storm ; at 71, a great storm ; at 88, a hurricane ; at 1 10, a hurricane that 

 tears up trees and throws down buildings. But, as I have already found 



* Essay on Heat. 

 Q 4 



