Cuar. IV.,§ 1] MECHANICS,—WATT. 869 
Of the applications of the steam-engine with which  (325-) 
Mr Watt was less immediately connected, its adap- Appl c 
tation to locomotion in the case of ships i in the last steam to 
century, and in that of railway trains in the present, navigation. 
by the inertia of the moving machinery, but chiefly 
by the continuous though constantly diminishing 
elasticity of the steam as it expands and fills the en- 
tire cylinder.' It is evident that, in the extreme case, 
Cornish 
engines. 
(324.) 
Their per- 
fection. 
the work required (in pumping) will be accomplished 
if the piston reach the end of the stroke just as its 
momentum is exhausted, and that, on the other hand, 
if the pressure of the steam remain constant through- 
out, the velocity will be a maximum just when the 
work being done by the machine is suddenly com- 
pleted, and so much moving power will be wasted. 
A medium distribution produces the most favourable 
result in practice, and it depends entirely upon the 
ratio between the resistance and the effective pres- 
sure of the steam what this most favourable propor- 
tion will be. In the single-pumping engines of Corn- 
wall, in which the economy of fuel is carried to the 
highest perfection, it frequently happens that not 
more than one-eighth of the stroke is performed un- 
der the full pressure of the steam, which acts expan- 
sively during the remainder of the stroke; but these 
engines, though condensing, are moved by steam of 
four times the elasticity of the atmosphere. The 
Cornish engines have been very elaborately perfected, 
and they have been more carefully tested in respect 
to performance than any others. It is perhaps not 
too much to say that they do not contain a single 
contrivance of any importance (beyond of course 
what they have in common with the atmospheric 
engine), which was not the unaided invention of Mr 
Watt. 
In the Cornish engine we see the Energy of Heat 
rendered available to an extent which the inventor 
himself would at one time have thought scarcely cre- 
dible. The combustion of a bushel of coal which in 
a Newcomen’s engine improved by Smeaton was 
capable of raising 3,000,000 pounds through one 
foot, in Watt’s improved pumping engine raised 
20,000,000 pounds the same height, But by the 
indefatigable skill and perseverance of engineers the 
Cornish pumps now yield at least jive times the last 
amount. This, however, is not the place to enter 
upon these details, nor can we stop to particularize 
the other and various mechanical inventions intro- 
duced by Watt in the form of valves, governors, and 
steam-indicators. Still less can we enlarge upon the 
endless and still multiplying applications of this ad- 
mirable moving power, which is as capable of super- 
seding the greatest natural forces hitherto applied by 
have been the most striking, and fraught with con- 
sequences the most important to mankind. Of the 
latter we shall have occasion to speak in a future 
section; of the origin of steam navigation we may 
here say a very few words. Passing over projects 
which never were realized, of moving barges by steam, 
or other inanimate power, against wind and tide,— 
such as those of Worcester, Papin, and Hulls,—we 
find that the first experiment entitled to be called 
successful was made by Mr Miller of Dalswinton in Miller— 
Scotland, conjointly with Mr James Taylor, tutor in Taylor. 
his family, who together formed the project of moy- 
ing vessels by means of paddle-wheels driven by a 
steam-engine, and realized it with the aid of Sym- 
ington, a practical engineer. As we shall also find 
in the case of steam-carriages, the idea of the applica~ 
tion of the steam-engine to move ships was already 
a familiar one to the minds of many persons about 
the middle of the last century. To put it in practice 
with advantage was the step required, Mr Miller's 
first boat was launched on Dalswinton Loch in Dum- 
friesshire, in October 1788, and attained a speed of 
five miles an hour. The subject was pursued by 
Symington and others. In 1789 a larger vessel was 
propelled on the Forth and Clyde Canal. Subse- 
quently, however, the invention languished. The 
want of co-operation, of capital, and ingenuity, na- 
turally extinguishes many valuable inventions, Watt 
himself was only rescued from the same difficulty by 
the unusual intelligence of Boulton and Small, his 
coadjutors at Birmingham, Symington was less for- 
tunate, as well as probably less meritorious; and 
though it is well established that Fulton, who passes 
on the other side of the Atlantic for the inventor of 
steam-ships, had seen the relics of Symington’s second 
experiment, we must do the Americans the justice to 
say that the application of steam to navigation first 
flourished in the United States, 
started a river boat with an engine of Boulton and 
Watt. In 1813 the example was tardily imitated on 
the Firth of Clyde. The subsequent improvements 
need not here be specified, They have been very 
great and striking, but with the exception of the recent 
substitution of the serew-propeller for paddle-wheels, 
they searcely involve any new principles.* 
In 1807 Fulton Pualton. 
man to the useful arts, as it is adapted by its easy 
regulation to replace human industry in the most 
delicate operations; “the trunk of an elephant, 
which can pick up a pin or rend an oak, is as nothing 
to it.??? 
We may briefly close what we have to say of Mr (326.) 
Watt personally, His health was feeble from child- eee 
hood, but being blessed with much calmness of tem- Wisk, 
per he prolonged his life to a great age, and passed 
through its struggles, though they were to him con- 
1 The double-acting engine was planned in 1774 or 1775. The expansion principle was first used in 1776 ; — parallel motion 
~~ atented in 1784.—Watt’s Notes on Dr Robison’s Article. Robison’s Mech. Phil., vol. ii. ® Lord Jeffrey. 
‘or farther details on the history of Steam =e see that article in the Encyclopedia ; and Mr Bennet Woodcroft’s 
wae on the subject, London, 1848. 
