REPORT ON METEOROLOGY. 
24 9 
are not sure that we shall gain much by assuming the gyratory 
theory of Mr. Mitchel *. 
We would recommend to any meteorologist taking up this sub¬ 
ject, to endeavour to establish observations at two stations, one 
considerably elevated above the other, and to trace the course of 
the wind at the two points when it is changing its direction : we 
know that currents in various directions several times super¬ 
posed often coexist in the atmosphere, and it is probable that 
changes of wind generally commence at considerable eleva¬ 
tions. 
Of all the columns of that too often unprofitable work, a 
meteorological diary, one of the most profitless has generally 
been that devoted to the direction of the wind, as in its usual 
form it does not admit of having any average taken, and there¬ 
fore remains an undigested mass of insulated observations. In 
order to draw any useful conclusion from this observation, we 
would therefore recommend the adoption of Lambert’s numeri¬ 
cal form, in which the south is denoted by 0°, and the angle is 
measured round the horizon by the W., N., and E. In this 
way S.W. is denoted by 45°, W. by 90°, &c. 
On the subject of Rain,— a very important one in a practical 
point of view,—we have not lately obtained much new informa¬ 
tion. The theory of Dr. James Hutton remains nearly unal¬ 
tered, only strengthened and enlightened by the clearer views 
of the nature of deposition which we now possess. The con¬ 
nexion of rain with the fall of the barometer has met with one 
elucidation from Mr. Meikle f which is worthy of notice, be¬ 
cause the change of pressure, it is shown, may be a cause as 
well as an effect. He observes that the expansion of air accom¬ 
panying diminished pressure being productive of cold, will 
diminish the elasticity of the existing vapour, and cause a de¬ 
position. 
M. Arago has collected many interesting facts in the phaeno- 
mena of rain J. He has traced the progress of decrease in the 
annual amount from the equator to the poles. It is now know n 
that on the Malabar coast in lat. 11^° N., not less than 123*5 
inches of rain fall in a year ; whilst in lat. 60° it is reduced to 
17 inches. The law of decrease is not known with accuracy. 
The author of the article Physical Geography in the Sup¬ 
plement to the Encyclopaedia Britannica §, has proposed the 
following formula for the fall of rain in inches : 
75 (rad. — sine lat.) + 8, 
* Silliman’s American Journal, xix. f Royal Institution Journal. 
X Annales de Chimie, xlii. 360; Annuaires du Bureau des Longitudes pour 
1824 et 1825, § vol. vi. p. 163. 
