438 Mr. Vivian^ on Meteorology. [May 22, 



The errors in medical and other works were referred to, es- 

 pecially in regard to the fall of rain, which is nearly double, both 

 in amount and duration, on Dartmoor as compared with the south- 

 eastern coast, from Exmouth to the Start Point, where the humidity 

 of the air is also proportionally less, being, as stated above, the 

 same in absolute amount with the average of England, and sensi- 

 bly less in the proportion of 7 to 9. The climate of that coast was 

 shown to be cool and dry in summer, but comparatively humid, as 

 Avell as warm, in winter, owing to the influence of the sea, which 

 retains a more uniform temperature, exhaling moisture in dry cold 

 weather, but acting as a condenser whenever its temperature is 

 below the dew-point of the air. 



A set of instruments were exhibited, which gave, approxi- 

 mately, the following results from one monthly observation : — The 

 maximum and minimum temperature; the maximum, minimum, 

 and mean humidity ; the greatest influence, and the duration of 

 sunshine ; the amount and duration of rain. The principle of most 

 of these was founded upon the atmometer, with a combination of 

 the wet and dry bulb and diflferential thermometers. By curves, 

 exhibiting the fluctuations of the barometer, and the character of 

 the weather, was shown how important it was to ascertain also the 

 hygrometrical condition of the atmosphere, the barometer frequently 

 rising before rains from the east. This diagram also proved how 

 little influence the moon exerts, and the fallacy of the generally 

 received opinion that its changes determine the subsequent character 

 of the weather. 



In conclusion, a narrative was given of a balloon ascent, illus- 

 trated by drawings of aerial phenomena, from sketches taken oi^ 

 the spot. The chief peculiarities of these were, the altitude of the 

 horizon, which remained practically on a level with the eye at an 

 elevation of two miles, causing the surface of the earth to appear 

 concave instead of convex, and to recede during the rapid ascent, 

 whilst the horizon and the balloon seemed to be stationary : — the 

 definite outlines and pure colouring of objects directly beneath, 

 although reduced to microscopic proportions, occasioned by the 

 absence of refraction and dispersion of the coloured rays when 

 passing perpendicularly through media of differing densities, which, 

 at an angle, produce aerial perspective :— the rich combination of 

 rays bursting through clouds, and having the sun's disc for their 

 focus, contrasted with shadows upon the earth which radiate from 

 a vanishing point on the horizon, the narrow shadows of clouds and 

 eminences, such as Harrow and Richmond, being projected several 

 miles, as seen in the lunar mountains : the magnificent Alpine 

 scenery of the upper surfaces of cloud, still illumined, at high alti- 

 tudes, by the cold silvery ray, contrasted with the rich hues of 

 clouds at lower levels, and the darkness of the earth after sunset. 



At higher altitudes than could be attained, and above the level 

 of perpetual congelation, were the beautiful cirrus clouds, com- 



