372 
EXPLANATION OF THE PLATES. 
metallic surfaces be diminished, the quantity of cold water or the capacity of the air- 
pump, or both, should be increased to produce the same effect. 
“ Haying now described the five several apparatus the combination of which (within 
proper proportions as hereinbefore described as regard the first three) constitute my 
invention, I proceed again to define and explain the extent of my claims. I now 
therefore state, I do not claim the exclusive use of any one of the five apparatus 
herein described taken separately, some of them, if not all, having been used before, 
nor indeed do I claim the use of any two of them, if unaccompanied bj" any or either 
of the others, but I do claim as my invention the exclusive use of the threefold 
combination of the sufficient quantity of metallic surfaces, the sufficient quantity of 
cold water passing among them, and the sufficiently capacious air-pump as herein 
before fully described, whether the said threefold combination be used alone or com 
bined with the distilling apparatus and the steam saver, or either of them. I 
also claim the exclusive right of combining the distilling apparatus and the steam 
saving apparatus, or either of them, with the above mentioned threefold combination, 
or even with the two first of them, videlicet, the metallic surfaces and cold water 
passing among them, should a less air-pump be used. In witness whereof,” &c. 
The advantages of Mr. Hall’s patent engines over injection engines will perhaps 
be best understood by his comparative statement of them. 
“COMPARISON BETWEEN INJECTION STEAM ENGINES AND SAMUEL HALL’S 
PATENT STEAM ENGINES. 
“ 1. Injection engines, when applied to 
steam navigation, comprise of necessity 
the barbarous practice of supplying dirty 
salt water to the boilers. 
2. In injection engines, the water in 
the boilers may become saturated with 
salt, in which case it will not boil under 
225° of temperature. 
3. In injection engines, in order to pre 
vent the water from becoming saturated 
with salt, a large quantity of boiling 
water must be pumped out of the boilers, 
or blown off, and replaced with cold water 
The patent engines effect a supply of 
the purest distilled water to the boilers, 
by which they are always kept in a 
perfectly clean state. 
The patent engines having pure dis 
tilled water in the boilers, it boils at 212° 
or at 13° less temperature than salt water, 
and of course requires less fuel to convert 
it into steam. 
The boilers of the patent engines never 
require any blowing out, no matter how 
long the engines are in uninterrupted 
operation.