respecting Climbing Boys in sweeping Chimnies. 107 
you my opinion upon the question of, How far it is practicable to 
supersede the practice of climbing boys, in sweeping chimneys by 
the use of machinery, I beg leave to say, that I am not able to’ 
give an opinion founded on much personal observation upon the 
subject ; but the result of the very particular inquiries, and of the 
numerous experiments which you have caused tobe made, prove, 
that machines, upon the principle of Smart’s, may be employed 
with success in all common cases ; but that the ball and brush 
let down from the upper part of the chimney flue is the only pro- 
cess which has answered in every instance. 
I have however learnt, from intelligent workmen in Scotland, 
where it has long been employed, that much injury is often occa- 
sioned by this operation at the turning of flues, especially where 
they are separated only by a thin wall; and I do not think it 
would be practicable, by any regulation, to provide for the con- 
struction of chimney flues in such a way as to obviate this im- 
portant objection. 
I am therefore led to believe, that, although the use of ma- 
chines may be very generally adopted, there is none hitherto in- 
vented which is so far free from objection in all cases, as to ren- 
der it possible wholly to dispense with the use of climbing boys. 
I have the honour to be, sir, 
Your obedient and faithful servant, 
Lieut. Col. Stephenson. (Signed) Ropertr SMIRKE, 
Office of Works, 11th January, 1819. 
Sir,—In obedience to the instructions, at various times re- 
ceived from you, on the subject of superseding climbing boys by 
the use of machines, I hereby inclose the result of the experi- 
ments made in consequence, with some observations and sugges- 
tions naturally presenting themselves in the detail. 
It appears, that the whole of the flues at present in use, may 
be comprised in four classes; the first and most numerous are 
those which are carried up in a perpendicular stack, the only bend 
in these flues being just sufficient to clear the opening of the flue 
above. The second, far less numerous, are those in which the 
fire-place is in a wall not continued higher than the next floor, 
and turning off with one bend (making two angles in the eleva- 
tion) to a partition wall, in which the shaft is continued to the 
top. The third, still less numerous, are those in which the shaft 
is at some distance from the fire-place, having at least one angle 
on the plan, and which of necessity forms two bends in the ele- 
vation. The fourth class, which forms a very small proportion 
of the total number already constructed, are those having more 
than one angle on the plan, and being, for a part of the length, 
entirely horizontal. 
For 
