Steam Engine. 351 
alternately opened and shut, by means of a floater which 
swims on the surface of the water contained in the bodj^ 
of the boiler. 
The second of the holes is the plate that closes the 
neck of the boiler, receives the lower end of another ver- 
tical tube, which serves to convey the steam from th$ 
boiler to the place where it is to be used. 
The third hole is occupied by a safety valve. 
This description shews that there is nothing new in the 
eonstruction or arrangement of the upper part of this 
boiler. In its lower part there is a contrivance for in- 
creasing its surface, which has been found very useful. 
The flat circular bottom of the body of the boiler, which 
as I said before is twelve inches in diameter, being pierced 
by seven holes, each three inches in diameter, seven cy- 
lindrical tubes of thin sheet copper, three inches in dia- 
meter, and nine inches long, closed below by circular 
plates, are fixed in these holes, and firmly ri vetted, and 
then soldered to the flat bottom of the boiler. 
On opening the communication between the boiler and 
its reservoir, the water first fills the seven tubes, and then 
rises to the cylindrical body of the boiler ; but it can 
never rise above si inches in the body of the boiler, for 
when it has got to that height, the floater is lifted to the 
height necessary for shutting the cock that admits the 
water. 
When the height of the water in the boiler is diminish- 
ed a few lines by the evaporation, the floater descends a 
little, the cock is again opened, and the water flows in 
again from the reservoir. 
As the seven tubes that descend from the flat bottom 
of the body of this boiler into the fire place, are surround- 
ed on all sides by the flame, the liquid contained in the 
boiler is heated, and made to boil in a short time, and 
with the consumption of a relatively small quantity of 
