132 
(4.) Such certainly never was, and never could have been 
the case, with any steamboat in which the wheels were made 
to turn by means of chains and rachet-work : — a sort of 
mechanism which may answer its purpose during an expe- 
riment, but which must rapidly wear itself out by shocks and 
rattling. Such an engine is not a “ practical steam engine; 
and a vessel driven by it is not a “ practical steamboat. 
Hence the importance which I am disposed to asciibe to 
the first actual use of a permanently efficient rotative steam 
engine to drive a vessel. 
(5.) It may be true that as an original inventor, Syming- 
ton ought to be ranked below his predecessors ; because Ins 
steamboat of 1801 was only a new combination of parts which 
had previously been invented separately by others: — the 
paddle-wheel, by some unknown mechanic of remote anti- 
quity; the application of steam to drive vessels, by a series 
of inventors, comprising Papin, Hulls, 1). Bernouilli, Jouftroy, 
Miller, and Taylor ; and the rotative steam engine by Watt : 
still the merit of having first used a “ practical steam engine” 
to drive a vessel is due to Symington. 
(G.) Considering the intimate personal knowledge possessed 
by Mr. Dyer of the early history of steam navigation, and the 
eminent services which he long ago did to the community by 
his efforts in promoting its introduction into Britain, it is 
very satisfactory to me to find that the main difference between 
us relates only to the degree of importance to be attached to 
a particular step in the history ot that art. 
I am, Sir, 
Your most obedient Servant, 
W. J. MACQUORN RANKINE. 
Glasgow, 11th Mat, 1863. 
