thermograph 
enables the temperature at any time during the week and 
the rate of variation to )>< iici'iin.tdy determined, (c) In 
the electric ci HI t;u-t mcthml a mercurial thennometer hav- 
ing a LITHC bull) and an iMilurjjfd sicm lu^ tin- upper end 
uf the mi" li'i't "| n, :MJI| M linr ]il;ii i in nil win- is made to 
dt'M-riid in tin- tllhc by clockwork at rri;ul:ir inN-rvuls. 
When the win: num's in mntac-i witli tin- top of the mer- 
cury, an electric circuit isclnsril, and tin- distant'*' i* iv- 
gistercd which the platininn win; hus di-si-nidrd in <>nl<T 
to touch the mercury mirfucf. This nu'Miud JH used in 
the instruments of Huiigli and ^ci-chi (/) In UP- manom- 
eter thermograph the actuating instrument is an air- or 
gas-tliermumeter. The vr^s.-l r.nit:iiniiiK air is conn* rtrd 
by a line lulu- with a rrgistcriug apparatus, of which vaii- 
ous forms have been duvlned. Changes of temperature 
produce changes of pressm v in tin- inclosed gas, and these 
change* of pressure are tin- subject of measurement and 
registration. The scale of the thermogrtun is evaluated in 
degrees either by a theoretical formula or by actual com- 
parisons. The instruments of Schreiber and Sprung be- 
long to this class. () A still further form, not belonging 
strictly to any of the preceding classes, is illustntt. .1 b> 
the Kit hard thermograph. Its thermometer is a Bourdon 
tube tilled with alcohol, to which is attached a lever car- 
rying the registering pen. With a rise of temperature 
the differential expansion produces a change of shape of 
the tube, accompanied by a corresponding change in posi- 
tion of the lever and registering pen. A high degree of 
sensitiveness and consequent accuracy Is attained by this 
instrument. 
thermography (thfr-mog'ra-fl), . [< Or. 6epfui, 
heat, + -yfxuftia, < ypfyetv, write.] Any method 
of writing which requires heat to develop the 
characters. 
thermo-inhibitory (thOr'mo-in-hib'i-to-ri), a. 
[< Gr. 0/v9. heat, + K. MWWtorjf.] Noting 
nerves whose function is to stop or inhibit the 
production of heat in the body. 
tnermojunction (ther'mo-jungk y shon), w. [< 
Gr. Oepfii?, heat, 4- K. j'tnrfiun.] The point of 
union of the two metals of a thermo-electric 
couple. 
thermokinematics (ther-mo-kin-e-mafiks), n. 
[< Gr. Qepfity heat, + E. kinematics.] The theory 
of the motion of heat. See the quotation. 
The science of heat has been called Thennotics, and 
the theory of beat as a form of energy is called Thermo- 
dynamics. In the same way the theory of the equilib- 
rium of heat might be called Thermostatics, and that of 
the motion of heat ThennnHnfmaticn. 
Clerk Maxwell, Heat, Int., i. 9. 
thermology (ther-mol'o-ji), . [< Gr. Mppi, 
heat, + -Aova, < Wywv, speak: see -ology.] The 
science of heat. 
M. Le Com to terms it |the science of heat] Thermology. 
Whetoell, 1'hilos. of Induct. Sciences, I. p. Uxii. 
6283 
ga 
thermolysis (ther-mol'i-sis), M. [< Gr. 
heat, + /./'Off, loosening, dissolving.] 1. Same 
The heat supplied has the effect of throwing the mole- 
cule into such agitation that the mutual affinity of the 
atoms cannot retain them in union. This is the process 
of Dissociation or Thermolysis. 
A. Daniell, Prln. of Physics, p. 319. 
2. The dispersion of heat from the body, by 
radiation, conduction, evaporation, and the 
warming of excreta and dejecta. 
thermolytic (ther-mo-lit'ik), a. and M. [< ttter- 
molyxix (-////-) 4- -iV.] I, o. Of or pertaining 
to thermolysis, in either sense ; heat-discharg- 
ing. Med. Nines, LII. 393. 
II. n. A substance or agent having to do 
with the discharge of heat from the body. 
thermolyze (ther'mo-liz), r. t. ; pret. and pp. 
therinoly-eti, ppr. thermolyzing. [< thermolysis 
(ct. analyze).] To subject to thermolysis; dis- 
sociate by the action of heat. 
thermomagnetic (ther'mo-mag-net'ik), a. [< 
Gr. drpftt/, heat, + E. magnetic.] Pertaining to 
the effect of heat as modifying the magnetic 
properties of bodies. 
thermomagnetism (ther'mo-mag'net-izm), n. 
[< Gr. Oepf"/, heat, + E. maijnetiitm.] Magnet- 
ism resulting from, or as affected by, the ac- 
tion of heat. . 
thermometer (ther-mom'e-ter), . [= F. tlnr- 
mometrv = Sp. termometre, termtimetro = Pg. 
tin rmiiiiii tro = It. tcrniomctro = D. G. Dan. ther- 
mometer = S\v. termouietcr, < NL. "therniOHie- 
trnm. <Gr. Sip/ty, heat, + /icrpov, measure.] 1. 
An instrument by which the temperatures (see 
temperature and Iherminui try) of bodies are as- 
certained, founded on the common property 
belonging to all bodies, with very few excep- 
tions, of expanding with heat, the rate or 
quantity of expansion being supposed to be 
proportional to the degree of heat applied, and 
hence indit-ating that degree. The expanding 
substance may be a liquid, as mercury or alcohol : a gas, 
as in the air-thermometer (which see); or a solid, as 
in the metallic thermometer (see below). The ordinary 
thermometer consist* of a slender glass tube with a 
small bore, containing in general mercury or alcohol ; 
this expands or contracts by variations in the tempera- 
ture of the atmosphere, or on the instrument being 
brought into contact vvilh any other body, or being im- 
mersed in a liquid or gas which is to be examined, ami the 
ate of the atmosphere, the body, liquid, or gas, with re 
rd to lir:ii, is imliratnl l>y a -Mir cither ajiplinl to the 
tutu- or i n^iaved on its exterior surface. The thermom- 
eter was invented by Galileo at some date prior to Hill, 
and was developed by his pupils through the flrttt thirty 
"!' Ilie .seventeenth century. In Kill tin- H'-renl MH 
nhilosophers wen- u.sini; a thei inometer consisting of a 
finlb Illlrd with ak-nliu], with sealed stem, and graduated 
on the stem according to an arbitrary scale, of which the 
divisions were, approximately, fiftieths of the volume of 
the bulb. Sagredo adopted a scale uf 300 divisions, like 
tin- ^i adini i-Hi ni a rjfelr, and fixed the application of the 
word dtijree to the thenuometrlc spaces. No means of 
o.inpuring observations made with thermometers con- 
taining different fluids and of different manufacture were 
possible until Fahrenheit adopted a graduation between 
two fixed temperatures. For the zero of hib scale Fahren- 
heit adopted the lowest temperature observed by him In 
the winter of 17UU, and for his upper fixed point he took 
the temperature of the body, ana marked it 90. By this 
system of numeration the temperature of melting Ice be- 
came 32, and the boiling-point of water 212. This is the 
scale of the Fahrenhrit th- rnnniieter commonly used by 
English-speaking peoplesand in Holland. Del'Isle, about 
1730, first used the melting-point of ice and the boiling- 
point of water as the fixed points of the thermometric 
scale, and they gradually came to be universally accepted. 
In lifaumw't thermometer (formerly largely used lu Ger- 
many and Russia, but now being superseded) the space 
between the freezing-point and the boiling point of WL.UT 
Is divided into 80 equal parts, the zero being at freezing. 
In the centiyrade thermometer, used widely throughout 
Europe, and very extensively In scientific investigations 
everywhere, the space between the freezing-point and the 
boiling-point of water is divided into 100 equal parts or 
degrees, the freezing-point being zero and the boiling- 
point 100*. The absolute zero of temperature is the logi- 
cal beginning of a thermometric scale, but since ther- 
mometric temperatures are primarily relative, the zero- 
point Is arbitrary, and the Fahrenheit, Reaumur, and 
centigrade thermometers present the different systems 
of numeration that have come into use. The following 
formula; give the conversion of these scales : Let F, R, and 
C represent any temperature as given hy the three scales 
respectively, then F = R x f H 32 s = C x $ + 32. The 
xtaiulard mercurial thermometer consists of a slender 
tube with capillary bore hermetically sealed at the top, 
and terminating at its lower end In a bulb tilled with 
mercury. The melting-point of ice and the boiling-point 
of water at standard pressure are determined on the 
tube, and the intermediate space is subdivided Into equal 
parts. The graduations are extended above and below 
the fiducial points, and finally the tube is calibrated, and 
outstanding errors of the graduation are determined. 
Ordinary thermometers covering any desired small range 
of temperature are graduated by comparison with a stan- 
dard. For extreme degrees of cold, thermometers filled 
with spirit of wine must be employed, as no degree of cold 
known Is capable of freezing that liquid, whereas mercury 
freezes at about 39 below zero on the Fahrenheit scale. 
On the other hand, spirit of wine is not adapted to high 
temperatures, as It is soon converted Into vapor, where- 
as mercury does not boll till its temperature Is raised to 
660 F. Mercury thermometers designed for measuring 
temperatures up to 400 C. (752* F.^are made by filling the 
stem and an upper bulb above the stem with nitrogen. 
The mercury expands against the increasing pressure of 
the nitrogen, and its boiling-point is raised thereby. Tem- 
peratures higher than this limit are usually obtained with 
air- or steam- thermometers and other forms of pyrometer 
(which see). The air- (or ga#-)thennometer consists of a 
quantity of pure dry air or gas contained in a reservoir such 
used (1) the constant-pressure thennometer. in which the 
gas is maintained at constant pressure and its varying 
volume measured ; (2) the constant-volume t/iennometer, in 
which the Increase of pressure under constant volume is 
measured. This is the ordinary form in which the in- 
strument is used. For accuracy it is decidedly superior 
to the mercury thermometer, and has been adopted as 
the ultimate standard to which all other thermometers 
are referred. In the metallic thennometer, as generally con- 
structed, temperature is measured by the change in form 
of composite metal bars, due to their differential expansion 
(hence more properly called bimetallic thennometer). One 
of the early forms was that of Breguet, which consists of 
a fine spiral bar made of platinum, gold, and silver. One 
end of the spiral is fixed, the other end being connected 
with a simple mechanical device to convert the curving 
or torsion of the bar under changes of temperature into 
the movement of an index over a dial having a scale mark- 
ed In a circle upon it The same principle, with variations 
In the mechanical application, is now much used in the 
construction of thermographs. For indicating very slight 
variations of temperature a thermo-electric Junction or the 
bolometer is employed. 
The thennometer discovers all the small unperceivable 
variations in the coldness of the air. 
0toM0tj Essays, ill. (an. 1676). (Jlichardton.) 
2. Hence, figuratively, anything which (rough- 
ly) indicates temperature. 
These fixed animals [corals], and the reefs which they 
elaborate, are among the best of living thermometer*. 
Gill, Proc. Biol. Soc. of Washington, 1885, II. 35. 
Aspiration thermometer, one in which the tempera- 
ture of the air is obtained by drawing air in with a venti- 
lating-fan through a tube, and causing it to flow rapidly 
over a thermometer, or over wet- and dry-bulb thermom- 
eters, placed therein. This method, first described by 
I'.elli In 1837, has been followed and developed in the in- 
strument of Assmann. Attached thermometer, one 
fastened to the tube of a barometer for indicating the tem- 
perature of its mercury. Axilla thermometer. See 
axilla. Bl-metal thermometer, a thennometer com- 
posed of a bar of two metals or alloys, having different 
rates of expansion, brazed t<igether and sometimes lout 
into the form of a spiral. The compound bar Is fastened 
riirictly at one end, the other end being connected with a 
simple mechanical device to convert the curving or tor- 
sion of the bar under changes of temperature into the 
thermometer 
movement of an index over a dial having a scale marked 
ui It. Celsius thermometer, a therm 
duced by Celsius In 17ttti<and used to a limited extent), in 
whieh the zero of the scale was placed at the ten. |. en, tin, 
of lioiling water and UK/ at the taOMntafad melting 
Id , plus ( + ) and minus ( ) degrees In llBMplMffa < m 
peiatuiuH heini: thus avoided. This wan a centigrade 
eii!e, I, nt nut that of tie ntigrade theiiiniin 
eter, which was introduced by l.innMi. Centigrade 
thermometer, see d.f. i. Chromatic thermom- 
eter, an arrangement of glass plates, .li \i-.i! hy sir 
i>avld Itrewster, exhibiting the <litteicnee bet \se-n their 
temperature and that of an object with which they are 
brought In contact by the different hues of 1 1 
light produced In the plates. Chromo thermometer, 
an instrument used to raise the temperature of petro- 
leum at the rate of 20* In fifteen minutes : used for pur- 
poses of tenting. Clinical thermometer, a small maxi- 
mum self registering mercurial thermometer used in oh- 
taining the temperature of the body. In IU usual form the 
range of scale Is 25' F., or less, and graduation li carried to 
one fifth of a degree. A very sensitive clinical Instrument, 
called the hutf-iniiititt thermometer, has a bulb of small di- 
ameter and an extremely fine liore. in which the mercury 
is rendered visible by a lens-fronted stem. Conjugate 
thermometer. Same as differential thermometer. 
Deep-sea thermometer, a registering tbermomuUT 
used to ascertain the temperature of the sea at any depth. 
The Instrument consists of the thermometer proper set In 
a metallic frame. The form of thermometer now used U 
that of Negretti and Zambra. It consists of a mercury 
thermometer whose stem, of wide bore, terminates In a 
small pyrlform sac. The stem Is contracted and con- 
torted just above the bulb, and when the Instrument is In- 
verted, the mercury -column breaks at this point, and flows 
down into the tube, which is graduated in the inverted po- 
sition. An overflow-cell prevents mercury from the bulb 
from entering the stem if there is a rise of temperature. To 
protect it from pressure, the thermometer U hermetically 
sealed in a strong glass tube, the part of which surrounding 
the bulb contains a quantity of mercury secured by a ring 
of india-rubber cement. By means of mechanism In Its 
frame, the thermometer is made to turn over at any de- 
sired depth, and the temperature at the instant of Inversion 
remains recorded in the tube until the Instrument is read 
and reset. For small depths, the instrument is reversed 
by a weight which is sent down the sounding-line. For 
great depths, the reversal is effected by means of the rev- 
olution of a small propeller, which is set in motion by the 
water so soon as the thermometer is drawn upward. 
Deville's air-thermometer, a form of air-thermometer 
used for measuring very high temperatures the thermo- 
metric substance, the air, being contained in a porcelain 
bulb capable of resisting the heat of a furnace. Differ- 
ential thermometer, an instrument for measuring very 
small differences of temperature. The earliest form, In- 
vented and named by Sir John Leslie, consists of a I -shaped 
tube, each end of which terminates in a bulb. The bend 
of the tube contains a colored liquid : the upper parts of 
the tube and the bulbs are filled with confined air. When 
one of the bulbs Is at a higher temperature than the other, 
the liquid in the adjacent stem is driven down by the high- 
er pressure, and rises in the opposite branch. The differ- 
ence in height is proportional to the difference in ternpera- 
t ure of the two bulbs. The instrument is now used only as 
a thermoscope. Earth-thermometr, one designed for 
ascertaining the temperature of the ground at different 
depths. Three types have been employed (a) a ther- 
mometer of large bulb and very long stem, so that, al- 
though buried many feet in the ground, the top of the 
liquid column extends above the surface (temperatures 
at depths of twenty feet have been obtained by this); 
(b) an ordinary thermometer inclosed in a wooden tube 
and other non-conducting packings, which can be sunk 
to any desired depth, the temperature of the thermom- 
eter being assumed not to change during the short time re- 
quired to draw it up and make the reading ; (c) (1 ) thermo- 
electric junctions; (2) the electrical-resistance method. 
Electric thermometer, (a) An apparatus for mea- 
suring small differences of temperature, based on the ac- 
tion of a thermopile. See thenno-eltctricity. (6) A ther- 
mometer whose action is based on the variation of elec- 
trical resistance produced by changes of temperature In a 
metallic conductor. The difference in the resistance be- 
tween a current passing through a conductor of known 
and one of unknown temperature gives the difference 
of temperature between the two. Also called differen- 
tial -remittance thermometer. The most delicate form In 
which the principle is applied is the bolometer. Fah- 
renheit thermometer. See def. i. Kinnersley's, 
thermometer, an apparatus sometimes used to illus- 
trate the sudden expansion of air through which a dis- 
charge of high-potential electricity has taken place. It 
consists of two connected tubes partially filled with wa- 
ter ; the larger one contains above the water-surface two 
knobs, and when the spark Is formed between them the 
water is forced up to a higher level In the smaller tub. 
Maximum thermometer, one that registers the maxi- 
mum temperature to whicn it is exposed. Three types 
have come into use in connection with the mercurial ther- 
mometer, (a) The Rutherford maximum has a light mov- 
able steel Index at the top of the mercurial column. The 
tube is placed horizontal, and as the temperature rises 
the mercury pushes the index before it. When the tem- 
perature falls, the Index Is left in situ to mark the po- 
sition of the maximum. (6) In Phillips s maximum, a 
small bubble of air makes a break in the upper part of the 
mercurial column. When the temperature beginsto fall, 
the detached portion of the column is left behind to regis- 
ter the highest temperature, (c) The N'egrettl maximum 
has the bore of the tube partly closed by a constriction 
just above the bulb. In rising temperatures mercury Is 
forced from the bulb past the constriction, but when the 
temperature falls the mercury cannot readily return to 
the bulb, and the top of the mercurial column indicates 
the maximum temperature. In order to reset the ther- 
mometer to the current air-temperature, the mercury is 
forced back into the bulb by whirling the instrument on 
a swing-pin. This form of maximum is used at the sta- 
tions of the I'nited state:- Weather 1:111 can. -Mercury 
thermometer. See def. i. Metallic thermometer. 
See def. 1. Metastatlc thermometer, a very sensi- 
tive mercurial thermometer, having an apical cavity 
