82 REPORTS ON THE STATE OF SCIENCE. 
The Marvin and Hergesell instruments are in general suspended from 
the wire some distance below the kite, so that the indications of the 
anemometer shall not be influenced by disturbances due to the kite. The 
Dines instrument is suspended in the centre of the kite, the anemometer 
thread being so long that the ball is out of range of the disturbances due 
to the kite. The method of attachment within the kite possesses consider- 
able advantages in protecting the instrument from injury. 
Ballons-sondes Meteorographs.—Of the different types of ballons- 
sondes meteorographs the first put into actual use was constructed by 
Richard. It was a baro-thermograph, having a multiple-cell aneroid 
barometer and a Bourdon tube thermometer filled with alcohol. The 
record was traced on a smoked sheet fixed to a clockwork drum. It was 
employed by Hermite and Besangon and by Hazen in 1893, and later, with 
various modifications, by Rotch at St. Louis, and in Russia. 
The first instrument employed by Teisserenc de Bort was a baro- 
thermograph consisting of an aneroid barometer and a small, slightly 
bent Bourdon tube alcohol thermometer. He found, however, that the 
aneroids showed considerable elastic after-effect,! and replaced them by a 
Bourdon tube barometer, which proved more consistent. The lag of the 
reservoir thermometer also led him to construct a metal thermometer 
whose thermal inertia was much smaller. This consisted of a strip of 
German silver 0-1 mm. thick, 250 mm. long, and 9 mm. broad, mounted 
in a nickel-steel frame, the expansion of the strip being multiplied two hun- 
dred times by a lever. In its final form his instrument consists of a 
Bourdon tube barometer, a bimetallic thermometer, and a_ hair 
hygrometer. The th rmometer is a compound strip of brass and steel 
soldered together. This strip has the form of a nearly closed ring, one 
end of which is fixed to the frame of the instrument, but insulated from it 
by a block of rubber, and the other is connected through levers to the 
recording pen. The block of rubber serves to prevent conduction of heat 
from the frame of the instrument, a source of error in previous instruments 
amounting to several degrees ©. The scale of the instrument is :— 
1 mm. of mercury = about 0°08 mm. deflection. 
Ibe (Op =  ,, 04mm. deflection. 
During an ascent the thermometer tube and the hygrometer hairs are 
exposed, but the rest of the instrument is enclosed in a cork case. The 
whole is slung by springs, inside a basket open at top and bottom, but 
lined round the sides with nickel paper. 
Hergesell designed a similar compound strip metal thermometer, but 
abandoned it owing to changes of zero produced by the straining of 
the soldered joint when the strip was distorted at low temperatures 
during the ascent. 
His final design included a Bourdon tube barometer, a hair hygrometer, 
and two thermometers. One of these latter is a bimetallic thermometer 
of the type used by Teisserenc de Bort. The other consists of a long, thin 
German-silver tube supported from its upper end by three nickel-steel 
uprights screwed into the base plate. The lever which operates the 
recording pen is fixed to the lower end of the tube, and is moved by the 
expansion or contraction of the tube. The tube projects through the base 
plate of the instrument, so that during the ascent a continuous current 
of air passes through it. The pressure, humidity, two temperature traces, 
1 Vide Compt. rend., July 11, 1898. 
