262 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
The following table shows the nature of the errors, and incidentally 
furnishes a comparison with one of the earlier ballon-sonde ascents: 
fal oem) Saleen 
Height (meters). a ie 
Glaisher.| Berson. and. Ballon: 
Siiring. | ~* i 
O=1 000 Rrrcscemataclcteisistaeiee erorsietainie lei cistererte aiarsicicieteerelseciaietaincie 7.5 5.0 Ue”? 8.3 
VOOO=2000: fare oo cs eroeteiaia.d Siarwisaiseye,o.e hm sisininteiee wie rsiaicleleie sles wioses of 6.5 5.0 6.8 6.1 
2OOO=SOO 0 arya a atararare Nata (of oYare ct (ol Nota ye iatatare alevolcieisis ete (eaicinisiersisioeisiots 5.0 5.4 3.7 4.2 
SOOO —LO0 Oras erecta eetance tere lero totey=te byeieie e istavelelee relate ae lowicjatats cltesersioteiste 4,2 5.3 5.2 5.1 
ANDO OOO eer ra mee etcpen cee ie ema ete to ateialeverers<ssieteie te eios nia elaeiererteceere 3.8 6.4 7.4 5.7 
HOOO=600 Or Boose co,ciwie wiatet cba ae eine hoe wielio aloe wares Sema ee ciae 3.2 6.9 5.5 6.3 
GO00=7000 2 Saas iar ah cic ac lnloc Siete mae lacie jaca we pacieermenieieee 3.0 6.6 We 4.7 
TOOO=SO0O = cate ers ict rates ace ave einer sais (e(ssrelace s cierereie avaio aie. s soainieleivic\ayswisizimnale 2.0 7.0 te? 7.6 
SOD0=0000 coe Bena se eee aetlacot Chena ee Asan ates eee aee 1.8 O10. ||) SG) | eeezat 
Temperature observations in manned balloons are now usually taken 
with an Assmann’s aspirator, in which a ventilating current of about 
4 m. p. s. is forced by a fan through a polished tube containing the 
thermometer and screening it from radiation. 
The instruments used with registering balloons are of two types. 
In the large type the record is made on a metal or photographic sheet, 
covered with lampblack, and wrapped round a revolving cylinder 
driven by a clock. Pressure, temperature, and humidity are recorded 
by separate pens. The barometer is a Bourdon tube or an aneroid, 
the thermometer some form of bimetallic instrument, and the hy- 
grometer a bundle of hairs. In the small type the temperature record 
is traced on a cylinder or plate, which is itself moved at right angles 
to the direction of motion of the temperature lever by the changes of 
pressure. The temperature and pressure are then given by the ordi- 
nates and abscisse of the trace obtained. The advantage of this 
arrangement is that no clock is required, and the instrument can 
be made much lighter and is more easily tested. The loss of the 
humidity trace is unimportant, because the hygrometric records at 
low temperatures are very untrustworthy, and the observations in the 
lower layers can be made with kites or manned balloons. 
The instruments used with kites are similar to the ballon-sonde 
instruments of the larger type, but they have an arrangement for 
recording wind velocity. In the Dines instrument the records are 
traced on a flat, circular sheet of cardboard rotated by means of a 
clock and resting on a wooden tray beneath which the instruments are 
placed. 
The ballon-sonde instruments are tested either (1) by keeping the 
thermometer at ordinary atmospheric pressure in testing for tempera- 
ture and the barometer at ordinary temperatures in testing for pres- 
