Agricultural Steam-Boilers, 
433 
The Discussion. 
Tho fitness of well-conducted and conscientious farm-labourers 
to be intrusted with the care and working of steam-engines, as 
stated by Mr. Holland, was illustrated from experience by Mr. 
Dent, M.P., Mr. T. Beale Brown, and Mr. Frere. In allusion to 
this svibject, Mr. Amos, C.E., said that when, after making a valuable 
engine for a gentleman present, he was consulted as to the choice 
of an engineer, he recommended that the engine should be placed 
in the hands of a steady-going labouring man, clean and particular 
in his habits, who would feel himself flattered by the trust reposed 
in him, and who, though he might know no more, perhaps, than 
was told him, would practise that little religiously ; whereas, if an 
engineer were employed, he might, perhaps, be often absent from 
the post of duty, and thereby cause delay and inconvenience. 
The causes of boiler explosions were variously stated. 
By Mr. Amos they were attribiited more to imperfect construction 
and careless work than any chemical cause : indeed, ho was quite 
sure that, if the explosions which had occurred had been more care- 
fully investigated and honestly reported on, nine-tenths of them 
would have been proved to arise either from some fault in the 
original construction, or from inattention in working. Accidents, 
^vhen they occur, are. too frequently made light of or glossed over. 
During dinner-hour the boiler is, perhaps, left with a strong coke- 
like fire under it, with the damper closed and tho door open. 
Under such circumstances, and more especiallj' so in the case of 
boilers not well constructed, the water might be lifted up in 
degree, and the starting of the engine or the injection of the force- 
pump might prove a disturbing cause. The steam might then be 
generated faster than it could be liberated by the safety-valve, and 
thus an explosion might ensue, though he was perfectly convinced 
that none of the explosions he had witnessed had so originated. 
Mr. Amos agreed with Mr. Holland that an engine-driver cannot 
be too careful in frequently moving the safety-valve to see that it is 
in good Older. There is a verj' good method of securing that object 
in use at the Crj'stal Palace. The safety-valve is so constructed 
that it is moved on the opening of either of the fire-doors ; and it 
is impossible to open the doors unless the safety-valve is all right. 
Professor Wilson, in reference to Mr. Eansome's rule (p. 430), 
suggested that it would be much better to open the valves before 
the water boiled than after boiling liad commenced, because the 
greatest risk of an explosion is at the moment when the water 
begins to boil. It is therefore desiiable to open the valve directly 
heat is employed, in order to ascertain whether or not all is right, 
particularly in cases where the fire has been drawn overnight, 
the boiler left charged with water, and the fire lighted uj) again 
next morning. 
Mr. Amos said, on opening the valve the air is first expanded 
by heat, and then it rushes out; so long as air is kept in the 
VOL. XXIII. 2 F 
