STEAM 
At the temperature 312° Fahr. 
f— 100 
100a zz 0-854121972 
10-000 zz — 0-208109100 
1-000-000 c zz + 0 005800000 
0-651812872 
1-477121300 
Log. of F J— 2-128934172 F'/ zz F 100=134-57 
Mr. Dalton's calculation.125-85 
Mr. P. Taylor’s experiment.159-45 
The disagreement between M. Biot’s formula and experi¬ 
ment, though trivial in the lower temperatures, increases 
rapidly in the higher. 
Dr. Urehasa formula admirably adapted to express the 
force of steam between 32° and 212° 
“ The elastic force at 212°, zz 30 inches, being divided by 
] -23, will give the force for 10 ° below; this quotient, divided 
bv 1-24, will give that for 10 ° lower; and so on progres¬ 
sively. To obtain the forces above 212°, we have merely to 
multiply 30° by the ratio 1-23 for the force at 222°; this 
product by 1-22 for that at 232°, and thus for each succes¬ 
sive interval of 10° above the boiling point. Thus 30 X 1'23 
— F 222 0 30 X 1 '23 X 1-22zzF 2 30® using F to denote the force 
at any temperature n, according to the notation of Laplace. 
“ By departing from the point 210° F, we shall obtain re¬ 
sults equally accurate and more convenient for comparison 
with the experiments of Dr. Ure; and it is observed, that 
this latter rule may be better adapted to give the elastic force 
corresponding to any given temperature moderately distant 
from 212 °. 
“Let r zz the mean ratio between 210° and the given 
temperature; n zz the number of terms (each of 10 °) distant 
from 210°; F, the elastic force of steam in inches of mer¬ 
cury. 
“ Then log. of F zz log. 28-9 + v, log. r; the positive 
sign being used above, the negative below 210°. Or by 
common arithmetic, multiply or divide 28 9 according as the 
temperature is above or below 210 °, by the mean ratio, in¬ 
volved to a power denoted by the number of terms. The 
product or quotient is the tension required. 
“ Example I.—The temperature is 140°. What is the cor¬ 
responding elasticity of the vapour from water heated to 
that point ? 
“ 140° is 7 terms of 10° each under 210 °; L26 is the 
mean ratio zz > a « d consequently r zz 1-26; 
£ 
71 — 11 . 
Log. 28-9 zz 1-46090 
Log. 1-26 X 7 zz 0-10037 X 7 z= — 0-70259 
0-75831 which is 
the logarithm of 5-732 inches - 
Experiment gives 5-77, leaving a difference of -04, 
which is inconsiderable. 
« Example II.—What is the tension of steam at the tempe¬ 
rature of 290° ? 
b23+H6 ,. ]95 B _ s 
“ 2 
Log. 28-9 zz 1-46090 
8 log. t zz 8 X 0 07737 zz + 0-61896 
2-07986 which is 
the logarithm of 120-02 inches —-- 
Experiment gives 120-15 
Vol. XXIII. No. 1590. 
ENGINE. 553 
« Example III.—Temperature 250°. Force of steam in con¬ 
tact with water ? 
r zz 1 ’ 23 + 1 : 20 — 1-215 71 zz 4 
2 
Log. 28 9 zz 1-46090 
4 log. r z 4 x 0-08458 zz + 0-33832 
1-79922 which is 
the logarithm of 62 - 98 inches ■ — — 
Experiment gives 61-90.” 
The history of the steam engine has already been given 
under the article Mechanics ; but we shall, in this place, 
introduce some particulars of a more detailed nature than those 
we have yet entered into, to shew that of the steam engine 
on its present principle, Captain Savary was, undoubtedly, 
the first inventor. 
The great elastic force of steam has been long known in 
the instrument called the aeo/ipile (see that article; and its 
property of condensation was also experienced in the use of 
the same instrument: the manner commonly practised for 
filling the ball with water being to plunge it into cold water, 
when heated and filled with steam ; by which means the 
steam is condensed, and forms a vacuum sufficient to draw 
the water into the ball, although the orifice is so small that 
water could not be introduced by any other means. At the 
same time, the true principles of its action were so little un. 
derstood, that the steam which issued from it, when placed 
on the fire, was supposed to be air produced by the decom¬ 
position of the water; and nearly all the old philosophers, 
who have described this instrument, proposed to employ it 
for blowing furnaces. The first idea of employing this force 
of steam to produce motion was by Brancas, a philosopher 
of Rome, who contrived a great number of different kinds of 
mills to be worked by the steam coming from a large aeoli- 
pile, and blowing against the floats or vanes of a wheel. 
We are obliged to this author for a number of other inge¬ 
nious inventions, which he dedicated to M. Canci, governor 
of Loretto, in 1623, and published his work (Le Machine) 
at Rome the year following. The force, however, which 
he could have thus obtained from steam would have been 
found altogether inconsiderable, if he had ever put it in 
practice. 
The earliest description which we have of a machine for 
raising water by fire, employed in raising steam from boiling 
water, is from the Marquis of Worcester, who, in the reign 
of king Charles II., and in the year 1663, published a small 
pamphlet, entitled “ A Century of the Names and Scantlings 
of the Marquis of Worcester’s Inventions,” written in 1655. 
This little work,-it appears, was addressed to the king aud 
parliament, and published with a view to obtain an encou¬ 
ragement from the public for the prosecution of 100 projects, 
which it details. No. 68 . of this Century, contains as fol¬ 
lows “ 68 . An admirable and most forcible way to drive 
up water by fire; not by drawing or sucking it upwards, 
for that must be, as the philosopher calleth it,- intrd sphee - 
ram activitatis, which is but at such a distance. But this 
way hath no bounder, if the vessel be strong enough: for I 
have taken a piece of a whole cannon, whereof the end was 
burst, and filled it three-quarters full of water, stopping and 
screwing up the broken end, as also the touch-hole; and 
making a constant fire under it, within twenty-four hours it 
burst, and made a great crack; so that having a way to make 
my vessels, so that they are strengthened by the force w-ithin 
them, and the one to fill after the other, I have seen the water 
run like a constant fountain stream forty feet high: one ves¬ 
sel of water, rarefied by fire, driveth up forty of cold water. 
And a man that tends the work is but to turn two cocks, 
that one vessel of water being consumed, another begins to 
force and re-fill with cold water, and so successively; the 
fire being tended and kept constant, which the self-same 
person may likewise abundantly perform in the interim be, 
tween the necessity of turning the said cocks.” 
This passage certainly contains a description of an engine 
for raising water by the repellent power of steam; and from 
7 B his 
