I have no idea if Watt had a patent on the steam governor. But I bet he didn't try to take one out on Boyle's Law.
I seem to recall that he tried to patent the idea of feedback - and was refused. He got the govenor patent though. I think the biggest problems are not so much in the extensions to the internationally accepted scope of patentability that the US patent office has uniquely indulged in in the past but the more recent accretions. Business models and experimental data are now being allowed - what possible justification can there be for giving the first person to mechanically sequence a piece of DNA exclusive commercial rights to exploit that knowledge. Ulitmately the US PTO has become an international object of ridicule and contempt. The PTO operates under a condition of moral hazard - it knows that it is likely to be sued for refusing a patent but cannot be sued for incompetently (or for that matter even maliciously granting one). One enterprising chappie even patented PEM - using the RFC as a reference in the claim! There are numerous examples of similar negligence. I can provide several examples of US patents issued with identical independent claims, in one case near identicaly worded. Rather than debate the PTO's actions of 20 years ago it would seem more appropriate to discuss their current actions. Phill