E X P 
125 
EXP 
fpreading out, of a body ; whether from any external 
caufe, as the caufe of rarefaction, or from an internal 
caufe, as elafticity. Bodies naturally expand by heat be¬ 
yond their dimenfions when cold ; and hence it happens 
that their dimenfions and fpeoific gravities are different in 
different temperatures and feafons of the year. Aii'com- 
preffed or condenfed, as foon as the comprefling or con- 
denfing force is removed, expands itfelf by its elaftic 
power to its former dimenfions. In Come few cafes, in¬ 
deed, bodies feem to expand as they grow cold, as water 
in the aft of freezing : but this is owing to the extrica¬ 
tion of a number of air bubbles from the fluid at a cer¬ 
tain time ; and is not a regular and gradual expanfion like 
that of metals, by means of heat. Mr. Boyle fays that 
ice takes up one 12th part more (pace than water ; but by 
Major Williams’s experiments on the force of freezing 
water, it has been found to occupy but about the 17th or 
18th part more fpace. (Trnnfkc. of the R. Soc. of Edinb. 
vol. ii. p. 28.) In certain metals alfo, an expanfion takes 
place when they pafs from a fluid to a folid ftate : but 
neither is this to be accounted any proper effeCt of cold, 
but of the arrangement of the parts of the metal in a cer¬ 
tain manner ; and is therefore to be accounted a fpecies 
of cryflallization. 
The expanfion of different bodies by heat is very va¬ 
rious ; and many experiments upon it are to be met with 
in the volumes of the Philofophical Tranfactions. In the 
48th vol. in particular, Mr. Smeaton has given a table of 
the expanfion of many different fubftances, as determined 
by experiment, from which the following particulars are 
extracted. The quantities of expanfion which anfwer 
here to 1S0 degrees of Fahrenheit’s thermometer, are ex- 
prefled in ten-thoufandth parts of an Englifh inch, each 
fubftance being 1 foot or 12 inches in length. 
White glafs barometer tube 
Martial regulus of antimony 
Bfiltered Heel - 
Hard fteel ----- 
Iron ------ 
Biftmith ------ 
Copper hammered - 
Copper S parts, mixed with 1 of tin 
Call brafs - 
Brafs 16 parts, with tin 1 - 
Brafs wire ----- 
Speculum metal - 
Spelter folder, viz. brafs 2 parts, zink 1 
Fine pewter ----- 
100 
130 
138 
147 
151 
167 
204 
218 
22 5 
229 
232 
232 
2 47 
2 74 
Grain tin - 
Soft folder, viz. lead 2, tin 1 
Zink 8 parts, tin 1, a little hammered 
Lead - 
Zink or Spelter - 
Zink hammered £ an inch per foot 
298 
301 
3 2 3 
344 
353 
373 
By other experiments it is found that, for each degree 
of heat of the thermometer, mercury, water, and air, ex- 
pstnd by the following parts of their own bulk, viz. 
Mercury the 9600th T 
Water the 6666th [-part of its bulk. 
Air the 435th j 
From thefe data it appears, that there is no general rule 
for the degree of expanfion to which bodies are fubjeCt 
by the fame degree of heat, either from their Ipecific gra¬ 
vity or otherwife. Zink, which is much lighter than 
lead-, expands more with heat ; while glafs, which is 
lighter than either, expands much lefs ; and copper, which 
is heavier than a mixture of brafs and tin, expands lefs. 
It ieems too that metals obferve a proportion of expan- 
iion in a fluid'ftute, quite different from what they do in 
a (olid one : for regulus of antimony teemed to fhrink in 
fixing, after being melted, confiderably more than zink. 
But of all known fubftances, thofe of the aerial kind ex¬ 
pand moft by an equal degree of heat; and in general the 
greater quantity of latent heat that any fubftance contains, 
V ol. VII, No. 413. 
the more eafily it is expanded ; though even here no ge¬ 
neral rule can be formed. It is indeed certain that the 
denfeft fluids, fuch as mercury, oil of vitriol, &c. are lefs 
expanfible than water, fpirit of wine, or ether. Which 
laft is fo eafily expanded, that were it not for the preffyre 
of the atmofphere it would be in a continual (late of va¬ 
pour. And indeed this is more or lefs the cafe with per¬ 
haps all fluids ; as it has been found, by experiments with 
the belt air-pumps, that waver, and other fluids, afc.end 
in vapours the more as the exhauftipn is the more perfeCt; 
from which it would feem that water would wholly rife 
in vapour, in any temperature, if the preffure of the at¬ 
mofphere were entirely taken off. 
After bodies are reduced to a vaporous date, their ex¬ 
panfion feems'to go on without arfy limitation, in propor¬ 
tion to the degree of heat applied ; though it may be im- 
poflible to fay What would be the ultimate effects of that 
principle upon them in this way. The force witli which 
thefe vapours expand on the application of high degrees, 
is very great ; nor does it appear that any obfiacle what¬ 
ever is infuperable by them. On this principle depend 
the fleam engines, fo much ufed in various mechanical 
operations ; likewife fome hydraulic machines ; and the 
inftrmrients called manometers, which fliew the variation 
of gravity in the external atmofphere, by the expanfion 
or condenfation of a lmall quantity of air confined in a 
proper veffel. On this principle alfo, perpetual move¬ 
ments might be conftruCted fimilar to thofe invented by 
Mr. Coxe, on the principal of the barometer. The ex¬ 
panfion of folid bodiesis meafured by an inflrument called 
the Pyrometer; and the force with which they expand is 
flill greater than that of aerial vapours ; the flame of a 
farthing candle produces an expanfion in a bar of iron ca¬ 
pable of counteracting a weight of 500 pounds. The 
quantity of expanfion howeveris fo ftnall, that it has never 
been applied to the movement of any mechanical engine. 
EXPAN'SIVE, adj. Having the power to fpread into 
a wider furfaee, or greater fpace.—Th’ expanjive atmof¬ 
phere is cramp’d with cold. Thomjbn. 
To EXPA'TI ATE, v.n. [ expatior , Lat.] To range at 
large; to rove without any preferibed limits.—Religion 
contracts the circle of our pleafures, but leaves it wide 
enough for her votaries to expatiate in. Addifon. 
He looks in heav’n with more than mortal eyes,. 
Bids his free foul expatiate in the (kies ; 
Amidft her kindred flars familiar roam, 
Survey the region, and confefs her home.. Pope. 
To enlarge upon in language.—They had a ctiflom of of¬ 
fering the tongues to Mercury, becaufe they believed him 
the giver of eloquence : Dacier expatiates upon thiscuftom. 
Broome. —To let loofe ; to allow to range. This fenfe, 
which is aCtive, is very improper.—Make choice of a fub¬ 
jeCt, which, being of itfelf capable of all that colours and 
the elegance of defignean poffibly give, (hall afterwards 
afford an ample field of matter wherein to expatiate itfelf. 
Dry den. 
To EXPE'CT, v. a. [expetto , Lat.] To have a.previous 
apprehenfion of either good or evil: 
Good with bad 
Expect to hear, fupernal grace contending 
With (rnfulnefs of man. . Elilton . 
To wait for ; to attend the coming : 
The guards, 
By me encamp’d on yonder lull, expert 
Their motion. Milton. 
To EXPE'CT, v. n. To wait ; to flay.—Elihu had ex- 
petted till Job had fpoken. Job. 
EXPECTA'BLE, adj. To be expected ; to be hoped 
or feared.—Occult and fpjritual operations are not expetta- 
ble from ice ; for being but water congealed, it can never 
make good fuch qualities. Brown. 
EXPEC'TANCE, or Expectancy, /'. The aCt or 
(late of expecting ; expectation.—Every moment is cxpec. 
tancy. Shake/pearc, 
Kk. But 
