340 Mr Bald on Steam^ and the Sediment of Water 
another mercurial thermometer was laid on the snow, it fell 
bfelow zero. 
Art. XXIV. — ^On Steam^ and the Sediment of Water found 
in the Boilers of Steam Engines. By Robert Bald, Esq. 
F. R. S. E. Communicated by the Author. 
In collieries where the common steam-engine is applied for 
drawing water from the mines, it frequently happens, that after 
a continuance of wet weather, the water accumulates so much, 
as to require the engine to be wrought night and day. If the 
boiler is supplied with water from the mines, it contains in this 
case a great quantity of earthy matter brought immediately 
from the surface, which renders the water within the boiler very 
muddy ; and there being little time for cleaning the boiler, ow- 
ing to the accumulated water in the mines, six or eight weeks 
sometimes elapse before this can be done. Towards the end of 
this period the water in the boiler is mixed with sediment to 
^such a degree, that the ordinary supply of steam cannot be 
raised, although the fire is increased in the furnace ; the conse^ 
quence of which is, that the common working speed of the en-r 
gine is greatly reduced. In this case it has been the constant 
practice of the engine-keepers in Scotland to apply a very simple 
remedy for increasing the quantity of steam. 
The substance employed is known by the name of Comings^ 
being the radicles of barley produced in the process of malting, 
which are separated before the malt is sent to market. About 
a bushel of these is thrown into the boiler ; and when the steam 
is again raised an immediate effect is visible ; for there is not 
only a plentiful supply of steam to produce the full working 
speed of the engine, but an excess of it going waste at the safe^ 
ty valve. This singular effect will continue for several days. 
Such is the factj^but the principles by which this vegetable 
matter acts, are not very obvious, as it is doubtful whether it 
acts chemically or mechanically. If its action is mechanical, 
chaff or saw-dust may produce the same effect. 
In the distillation of ardent spirits upon a great scale, it is 
found necessary, when converting the fermented liquor or wash 
