320 
MR. J. WELSH’S ACCOUNT OF METEOROLOGICAL 
and altitudes taken by Mr. Glaisher show that at 2^ 44“ when the height was 
11,000 feet, the balloon was 5 miles S. by E. of Greenwich Observatory. The 
grratest elevation (22,930 feet) was reached at 3^^ 16 ”p.m.; about which time the 
clouds, which had hitherto obscured the earth, had disappeared, and we perceived 
that the balloon was rapidly approaching the sea. Mr. Green discharged gas 
copiously, and the descent became very rapid; a landing being effected within 
4 miles of the sea, accompanied by a considerable shock which broke several of the 
instruments. The descent took place, between 3** 40“ and 3^ 45“, at Acryse near 
Folkstone, about 57 miles E.S.E. from London. The time occupied in moving from 
a little S.W. of Vauxhall to 5 miles S. by E. of Greenwich, or about 9 miles, was 
18 minutes; the remainder of the distance to Acryse, about 50 miles, being accom- 
plished in from 55 to 60 minutes, or at the rate of fully 50 miles an hour. 
As the height reached on this occasion was considerably greater than in the pre- 
vious ascents, the effect of the diminished pressure was more severely felt ; both Mr. 
Green and myself having experienced considerable difficulty in respiration, with 
much breathlessness and fatigue after any muscular exertion. 
^ 4. Description of the Table of Observations. 
All the meteorological observations taken during the ascents are contained in 
Table I. 
Column 1 contains the times at which the observations were made. Column 2 
contains the readings of the thermometer attached to the barometer. Column 3 con- 
tains the observations of the barometer corrected for temperature, by Schumacher s 
tables, and for scale error. The numbers, to which the mark is affixed, in the 
observations of August 17 and 26, are the occasional readings by myself of the 
second barometer. The readings of the barometer were made by estimation to 0-01 
inch ; but the probable error of an observation, from various causes,— such as rapid 
change in the height, and the occasional oscillation of the mercury from agitation ot 
the car,— is perhaps 0-03 inch, or even sometimes more. This degree of accuracy 
appears, however, to be quite sufficient with reference to the changes of the tempera- 
ture and humidity ; an error of 30 or 40 feet in the resulting height being equivalent 
in general to a change of only one-tenth of a degree of tempeiatuie. 
Column 4 contains the height above the level of the sea, as deduced fiom the 
barometric readings by the formula of Laplace. The formula actually employed was 
2 = log X 18336^1 +0-002837 cos 2L) ^1 + 6366200 ) * ’ 
or expressed in English feet and Fahrenheit s degrees, 
log X 60159(^1 +^^gQQ^ ) +0-002837 cos 2L) (l +2088690 o)’ 
where 2 is the height required ; h and h', t and t’ the height of the barometer cor- 
* Annuaire M6t6orologique de la France, 1849, page 54. 
