434 
Patents^ 
him, as well as his own ; if he does, the patent is void. If the ad- 
dition be to a machine or manufacture already patented, the last 
patentee cannot use the first without license, or the first patentee 
use the addition without license. 
Sthly. It does not seem fully settled, whether a patent can be 
supported for an abstract jirincifile however new. Judicial opi- 
nions are divided on this head. Thus, the Marquis of Worcester 
in his Century of Inventions, mentions one, of an engine which can 
be set to work and kept at work by the mere force of steam aris- 
ing from boiling Water. Would the Marquis have been entitled 
to a patent, for the exclusive use of all engines and machines 
whereof the moving power w'as the force of steam ? 
The better opinion seems, not. The ways and lueans, the 
method or variety of methods, and the machinery, by which steam 
can be applied as a moving power, seems legally requisite to be 
set out, previous to the establishing of such a patent. Otherwise 
the public may rest in doubt whether this can be done ; moreover 
the patentee who conceals his method of doing it, is hardly entit- 
led to a patent. 
But where the method of effecting this, is plain and obvious 
to an artist of common skill, so as not to need a particular descrip- 
tion, the want of it will not vitiate the patent. Thus, the patent 
of Boulton and Watt, was finally established for condensing the 
steam in a reservoir or box at a distance and separate from the 
%vorking cylinder; although the precise method employed by 
them was not described. I am however not prepared to acqui- 
esce in this much litigated decision, without great hesitation. 
Perhaps if the method actually employed were described, it would 
so far satisfy the law, as to cover any other after-found method 
of putting in practice the same principle. But I offer this in 
great doubt. 
Upon this head, it is worthy to be considered, that if a patent 
can legally be supported for a principle merely, no improvement 
however important in the method of putting it in practice, can 
be used during the existence of the patent-right. The monopoly 
is not merely a pecuniary tax on the community, but an obstacle 
iilso to future invention. Thus, if a^atent had existed for the 
principle of raising water, or moving machinery by means of 
steam, and Savary’s method had been used— -none of Watt’s im- 
provements could have been brought into use during the patent- 
term. Hence the propriety of confining the patent to the method 
of doing the thing. Hence also patents are properly granted for 
