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below.  Rather, the established practice reflects the understanding that only processes 
related to manufacturing or “manufactures” were within the statute.  The English cases 
before 1793 recognized that the practice followed in issuing patents was directly 
relevant to the construction of the statute.  See, e.g., Morris, 1 Carp. P.C. at 34 
(declining to read the statute in such a way that “would go to repeal almost every patent 
that was ever granted”).  
Third, nearly contemporaneous English cases following shortly after the 1793 Act 
lend further insight into what processes were thought to be patentable under the English 
practice at the time the statute was enacted.  Although the issue of the validity of 
process patents had not conclusively been settled in the English common law before 
1793, the question was brought before the courts in the landmark case of Boulton v. 
Bull, 2 H. Bl. 463, 465 (C.P. 1795), which involved James Watt’s patent for a “method of 
lessening the consumption of steam, and consequently fuel in [steam] engines.”
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    In 
1795, the court rendered a split decision, with two judges on each side.  Boulton, 2 H. 
Bl. at 463 (1795).  Those who viewed process patents as invalid, as did Justice Buller, 
urged that a method was merely an unpatentable principle: “A patent must be for some 
new production from [elements of nature], and not for the elements themselves.”  Id. at 
485.  He thought “it impossible to support a patent for a method only, without having 
carried it into effect and produced some new substance.”  Id.  at 486.  Justice Health 
similarly found that the “new invented method for lessening the consumption of steam 
                                            
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The Supreme Court has in several opinions noted Boulton v. Bull in 
connection with its consideration of English patent practice.  See, e.g., Markman v. 
Westview Instruments, Inc., 517 U.S. 370 , 381 n.6 (1996); Evans v. Eaton, 20 U.S. (7 
Wheat.) 356, 388 n.2-3 (1822). 
 
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