258 REPORT — 1844. 



In Plate XXXIX. these numbers are arranged upon the circumference of 

 eio-ht concentric circles, divided into eight points of the compass, so as to 

 exhibit the routine of these elements under a circular form and in the 

 order of the letters denoting them. Now by reference to this scheme, it may 

 be perceived, that the integral amount of wind increases from a minimum at 

 north-east, in passing round the circle by the south, to a maximum at north- 

 west, after which it again decreases. The mean pressure in pounds on the 

 square foot, and the mean velocity in miles per hour, do not vary for each 

 direction more than might have been anticipated, the limits of the mean 

 pressure being from -5 of a pound to 2'5 pounds, and the velocity from 18 to 

 26 miles per hour. 



The temperature of the air with these different directions of wind decreases 

 from a maximum at south to a minimum at north-east in going round the 

 circle by the west, after which it again increases. 



The atmospheric pressure, on the contrary, proceeds in an opposite order. 

 It increases from a minimum at south to a maximum at north-east in passing 

 round the circle in the same direction, after which it again decreases. Thus 

 when the temperature is greatest the barometric pressure is least. 



The amount of rain increases from a minimum at north-east, in passing 

 round the circle by east, to a maximum at south, after which it again de- 

 creases, being a course similar to that of the temperature. 



Such are some of the results of the discussion of the observations made at 

 Plymouth and Devonport with Whewell's and Osier's anemometers, and al- 

 though we cannot consider them perfect, yet they are still most useful ap- 

 proximations, and fully show, that whatever may be the imperfections of these 

 instruments, they comprise the elements of a valuable method of investigating 

 the phaenomena of winds by experimental means; and there can be, I think, 

 but little doubt, that if a very perfect instrument involving these elements, 

 were observed for a long series of years, most important information relative 

 to the great periodical and other movements of the air would necessarily 

 result. 



It is not without much satisfaction I have to state that Mr. Osier has lately 

 so much improved his anemometer that all the great imperfections are quite 

 remedied, so that we now really possess a machine calculated to furnish a 

 constant register of the direction and pressure of the wind. One of these 

 instruments is now at work on that splendid building, the Royal Exchange, 

 in London. The vane is no longer subject to the violent and irregular oscil- 

 lating motion so common to vanes of the ordinary kind. In this new arrange- 

 ment the pressure-plate is kept to its work by means of a small windmill-fly 

 acting on a cog-wheel, similar to that on which common windmills are turned 

 to the wind. The pressure-plate is of increased dimensions delicately hung 

 on radius rods, and brought to act on a series of spiral springs, by which the 

 least and greatest forces are registered, and that without any disturbing os- 

 cillation. These, with sundry other improvements in the mechanism and the 

 method of registering the results, have certainly rendered the use of this in- 

 strument most important to meteorology. 



