336 NATURE 
impression. Such an achievement with the larger 
instruments would have cost more than 5ool. in in- 
struments alone. 
When sending up one of the Continental instru- 
ments it is usual to have two balloons made of rubber 
fabric, one being givenrather more lift than the other 
the instrument, placed on a bag of nickel paper, 
open 
FiG. 7-—Trace and cali- 
bration marks, Dines 
meteorograph. 
Fic. §.—Sounaing balloon with parachute. 
at both ends, to protect it from the direct rays of the 
sun, is slung below the balloon. The balloons ascend 
until one of them bursts; the remaining balloon 
cannot support the instruments, but it has sufficient 
lift to allow them to descend gently and without 
injury to the earth’s surface. In the case of ascents 
made at sea a float is attached below the instruments, 
and the unburst balloon, which has not been given 
enough lift to support the float and the instruments, 
has sufficient lift to keep the instrument clear of hie 
water. The unburst balloon, whether on land or at 
sea, is a signal to show where the instrument has 
descended. Sometimes only one balloon is used, but 
in this case it is necessary to have a parachute so 
arranged that when the balloon bursts the parachute 
will come into action and bring the instruments down 
in safety. Mr. Dines’s meteorograph is so light that 
the fabric of the burst balloon is sufficient to check 
‘Teisserenc de Bort’s observa- 
Fic. 9.—Captive balloon at M. 
tory at Trappes 
the velocity of descent; and these instruments have 
over and over again fallen from heights of ten miles 
or more with no ill result whatever. 
M. Teisserenc de Bort used paper balloons; and 
that they might ascend at a regular pace they carried 
a sandbag with a hole in it, so that the balloon was 
always dropping ballast. In order that the balloon 
might not float at the greatest height attained, there 
NOY 2326. -vOl 203) 
was an arrangement actuated by clockworl whereby 
after a certain time a hook tore a rent in the lower 
part of the balloon, while the upper part became 2 
parachute which allowed the instruments to fall 
slowly. 
Small captive 
for lifting instruments 
desired to explore t 
or so; but they cannot attain 
as they have to lift the wire 
balloons have been used with success 
in calm weather, when it is 
the air up to heights of a kilometre 
any very great height, 
that holds them; 
they 
Fic. 10.—Landing the captive balloon. 
are apt to become very unmanageable if even a slight 
wind gets up while the flight is in progress. In 
Germany and Austria the balloon-kite has been used 
with success; it is a captive balloon of a form so 
designed that the wind lifts it instead of depressing it, 
as it does an ordinary captive balloon, 
A balloon in its ascent gives us more information 
than merely the temper ature and pressure of the air 
through which it rises. If we watch it we see it 
moving in varying directions as it passes through 
different currents of air 
in its ascent. We have 
only to watch the 
balloon through the tele- 
scopes of theodolites to 
obtain its real path 
through the atmosphere, 
from which may be de- 
duced the wind velo- 
cities and directions in 
the various layers. For 
this purpose we may 
use balloons — scarcely 
larger than a_ child’s 
air-ball, and, given a 
clear sky, we - may. 
follow such balloons up 
to heights of 5 or 6 km. 
The larger balloons used 
. ee Fic. 11.—Austrian military balloon 
for carrying instruments kite. 
can be followed with the 
and I have 
of. ten 
a hori- 
eater distances ; 
burst at a height 
theodolite for 
myself seen a_ balloon 
miles above the surface of the earth and at 
zontal distance of forty miles. 
For observing balloons in this way a special theodo- 
lite is advisable, for the ordinary pattern, when used 
for high angular altitudes, necessitates extremely un- 
comfortable attitudes on the part of the observer. 
Various ingenious pieces of apparatus have been 
much gre 
a 
