BALLOON ASCENTS. 
407 
To make observations on sound. 
To make physiological observations. 
To note atmospheric phenomena in general. 
To attain these objects, it was necessary to think well in 
respect to the kind and character of the instruments to be 
used, as well as to their arrangement for use. 
The instruments, of necessity, must be of extreme accuracy 
and dehcacy ; and upon their convenient arrangement, in so 
confined a space as the car of a balloon, a great deal was 
dependent. The kind of instruments used, and their arrange- 
ment in the car of a balloon, are shown in Plate XVI., as 
prepared for observation. 
Xear one end of the car was placed a board or table, the 
extremities of which rested on the sides of the car, and were 
tied to it. Upon this board were placed suitable frameworks 
to carry the several instruments, arranged as shown in the 
Plate. At the extreme left hand (1) is shown a blackened- 
bulb thermometer with its bulb in a vacuum tube ; just above 
it (2) is placed a very delicate blackened-bulb thermometer — 
both these instruments were exposed to the full rays of the 
sun; at (3) and (4) were placed dehcate dry- and wet-bulb 
thermometers, these instruments were covered with double 
highly-polished silver caps, in the form of a frustum of a cone, 
open both at top and bottom ; that for the dry-bulb is shown 
at (5), being removed to show the form of the bulbs of these 
thermometers; that for the wet-bulb is placed in situ. At 
times, additional protection was applied to these instruments. 
Prom the wet-bulb (4) the conducting thread is seen passing 
from the muslin covering the wet-bulb beneath the silver cone 
to the water vessel (6), from which water was conveyed to the 
wet-bulb thermometer. The next instruments in order are a 
similar pair of dry- and wet-bulb thermometers (7 and 8) : these 
were inclosed in two silver tubes placed side by side,, and 
connected together by a cross piece joining their upper ends, 
and over both were placed double shades with spaces between 
them (not shown in the Plate), as in the other pair of 
thermometers. In the left-hand tube was placed the lower 
end of the stem and bulb of the dry thermometer ; and in 
the right-hand tube, the same parts of the wet-bulb thermo- 
meter ; towards the lower end of the left-hand tube there was 
an opening ; by means of the aspirator, to be spoken of 
jDresently, a strong current of air was drawn in at this aperture, 
then passed the dry-bulb, in its upward passage into the small 
horizontal tube, and from thence into the right-hand tube, 
passing downwards over the wet-bulb, and away by the flexible 
tube to the aspirator under the table. Xear to these instru- 
ments was placed a watch or chronometer (9) adjusted to Green- 
