24 REPORT—1849. 

On the Means of Computing the Quantity of Vapour contained in a Vertical 
Column of the Atmosphere. By T. Horxtns. 
Mr. Hopkins showed that the quantity of aqueous vapour existing in the atmo- 
sphere is computed, by meteorologists of the present day, from the tension of vapour 
near the surface of the globe in such a way as would be correct if an atmosphere of 
vapour only existed. But the vapour in our atmosphere is intermixed with and 
diffused through gases, which gases cool by expansion consequent on the removal 
of incumbent pressure five times as much as the vapour does. ‘The vapour therefore 
produced by evaporation at the surface of the globe, as it passes into the higher 
regions of the atmospheric space, is cooled and condensed, not by its own law of 
cooling by expansion, but by the cold of the gases; and the result is that a smaller 
quantity of vapour remains in the atmospheric column with a given temperature 
and dew-point at the surface than there would be in a pure vapour atmosphere, or 
than is now said to be indicated by the tension of the vapour found at the surface. 
That tension he showed was a consequence, not alone of the pressure of an incum- 
bent column of vapour, but also of the resistance which rising vapour encounters 
from having to penetrate the gases while expanding upwards into the atmospheric 
space. As soon as elastic vapour is formed the surface of the globe becomes the 
base on which it rests, and from which it is disposed to expand upwards. But the 
resistance of the gases prevents free expansion, and preserves a certain amount of 
density of vapour that would not otherwise be so early attained. The tension of 
vapour therefore only measures the degree of density that is thus produced, and 
does not indicate correctly the quantity that exists in the whole atmospheric column. 
Tables were exhibited by Mr. Hopkins to show the quantities of vapour, expressed 
in decimal parts of an inch of mercury, that could exist at different heights to the 
extent of 4000 yards from the surface, in an atmosphere of pure vapour, and also in 
our mixed atmosphere, each being at the temperature and dew-point of 50° at the 
surface. And the excess in the quantity of vapour in the former above the latter 
was stated to show the extent of the error involved in the present mode of estimating 
the quantity of vapour in a vertical column of the atmosphere with the dew-point 
named, 50°. 

On Meteors. By Epwarp Joseru Lowe, F.R.A.S. 
See Reports in this volume, page 1. 

Notice of a Meteor seen in India on the 19th of last March. 
By Admiral Sir C. Matcoum. 
This consisted of selected notices of the meteor from the Bombay Times of March 
and April, and contained several letters detailing the circumstances under which it 
was seen by the different writers—from which it was inferred to be a mass of over 
600 feet in diameter; and the place at which it fell after bursting was ascertained 
to a high degree of probability : it fortunately was not an inhabited place. 
Extract from the Bombay Times, March 16, 1849. 
We have letters from Hoshungabad to the 6th inst., which mention that most 
extraordinary weather had prevailed there during the latter half of February. It 
had been close, hazy and dry, and a similar state of matters prevailed up to the 
day above mentioned. On the evening of the 5th the clouds began to collect, the 
atmosphere having been highly charged with electricity for four days previous,—the 
electrometer (Cavallo’s) readily indicating the amount, and the least friction causing 
considerable excitation. Pressure and dryness had somewhat increased, and rain 
was therefore not looked for, but either another earthquake or a thunder-and-dust 
storm was predicted by the weather-wise. On the 20th of February half a gale 
had blown throughout the greater part of the day, the mean of the barometer ha- 
ving descended in three days from 29°949 to 29°684! Our correspondent continues : 
“« Prognosticating an earthquake at Hoshungabad is somewhat akin to a pig see- 
ing the wind; but I only hint at such a phenomenon from the consciousness that 


