374 ^tearn Engine. 
pies and properties as in Fig. 3. which I suppose needs 
•fto explanation. 
Fig. 4, is a lever constructed by an eminent engineer in 
Hungary some years since, which possesses a very great 
f degree of support by the king post and iron braces, but 
does not, in my opinion, discover so much science as the 
two preceding ones. I forgot to observe, that inner 
arches may be attached to Fig. 1. without materially af« 
fecting its principle, if tliey are well let on the whole fram- 
ing, and bolted to each other without passing through 
the scantles. 
I am. Sir, 
Your most obedient Servant^ 
J. C. HORNBLOWER. 
East RoWy City Road^ Tuesday ^ May 11 , 1802. 
(2 Nich, Journ. 68, J 
Letter from Davies Giddy, Esq. M. P. describing a sin- 
gular fact of the invisible emission of steam and smoke 
together from the chimney of a furnace ; though either 
of them^ if separately emitted^ is visible as usual. 
To Mr. NICHOLSON. 
Si^, Clifton^ August 6, 1805i 
TRAVELLING, and a variety of occupations, have 
hitherto prevented me from sending you aii account of the 
circumstances observed by myself and others, during the 
working of an engine on Mr. Trevethick’s construction, 
at Merthyn Tidwell in South Wales, and which I had the 
pleasure of relating to you, some time since, in Soho | 
Square. I now transmit a statement of the facts, avoid- i 
ing all comments or attempts at explanation. j 
Mr. Trevethick having adapted his steam engine to the 
purpose of moving waggons^ contrived every accessaty 
part as light as he possibly could, and as little inconve- 
nient to persons who might assist, or witness an experi- 
ment. The flue for conveying off the smoke, and affords 
