Well, the M'Harry 1809 distilling book came. Very interesting book. I think John put his finger on the part that relates to what we talk about here, i.e., origin of charred barrel aging and maybe bourbon. I'll try to post a full review of the book in the book review section (I've been busy at work including part of weekends), but I'll say here I don't think there is any question that term "branding" meant firing the barrels inside. The book is too early to speak of branding in any modern sense. The very word "branding" means evidently burning (it is an alternate spelling of the word burning). "Brandy" means Burnt Wine and my this gets interesting because generally it has been said brandywine (origin of the term brandy) comes from the term burned wine, i.e., boiled wine. Wine (and cereal beer) are boiled of course to make spirit but is it possible the term brandy is related to the idea of spirit being matured in burned barrels, and so meaning burned wine in that sense? This would bring closer to the origin of bourbon the idea that John suggested of brandy practice being at the root of bourbon development (since cognac and probably European brandy in general is aged at least for part of its life in new charred barrels, this is unquestioned). What a tangled web! But in any case, this casual reference in the book to branding barrels is intriguing and may be at the origin of bourbon development. Not that it started it, but it seems clear M'Harry (and probably Elija Craig and others before M'Harry) knew that storing whiskey in new charred (or probably any-charred) barrels imparted desirable flavor and color. M'Harry passes on an idea but he doesn't claim to have invented it (whereas he makes that claim for his method of yeast propagation and management). M'Harry in other parts of the book states casually that "aged" or "old" whiskey has a particular taste (which he doesn't describe). He doesn't talk about aging as a methodical practice though, in fact if anything he ignores the whole aging issue other than, (i) where he talks about how to emulate aged whiskey by various means, e.g. by adding burned sugar or parched wheat (Byrn may have picked up his references to that from M'Harry), and (ii) his aforesaid reference to the branding of barrels to deliver a superior article to consumers. The part John cited, where M'Harry says the producer that follows the practice will have a significant leg up on the competition, is written in a tantalizing almost coy kind of way, as if M'Harry knew he was on to the something and sooner or later someone would market whiskey regularly aged in charred containers and make a killing. Probably this was local lore here and there in Pennsylvania (where M'Harry lived, there is no reference to Kentucky) but as I say although the writer may have realised distilling was on the cusp of something significant for the most part he seems to assume whiskey will be drunk new or fairly knew. I infer from the book that the benefits of aging whiskey in charred barrels was discovered accidentally, as a side wind from the process of burning barrels to sanitize them.
His discussion about mash bills is very interesting. Generally he is only concerned with yield and whether the slops can be good feed for cattle and hogs. E.g. he says hogs prefer slops that were made from a mash that does not use too much rye but where there was a certain percentage of corn. Another factor he is concerned with is how easily the grain can be mashed. He concludes that the best approach is half rye and half corn (with some barley malt for conversion, he states that specifically). The reason he gives is, the grains are easier to mash whereas, say, an all-corn mash is hard to work, to "scald") . And it is here, in the 50/50 mash bill discussion, that I saw the one time he refers (albeit indirectly) to the effect of a mash bill on taste, he says the 50/50 way of working is not just ideal in economic terms but also is good for "the whiskey". Clearly he means it tastes better made with a 50/50 mash of rye and corn than if made with the same grains in different proportions. Otherwise he never talks about taste (as opposed to purity, but that is different, e.g. he is concerned continually to avoid making a whiskey that tastes musty or sour, say from bad yeast, or is too turbid). He is concerned also in general to tell people how to make spirit from what is available, which shows how things were different then. But his 50/50 corn/rye mash discussion would mean his whiskey might have tasted like, say, Pikesville rye does today, or Rittenhouse, or the original Michter's Sour Mash (which was 50% rye, 38% corn). I was going to say Wild Turkey rye too but to me the current one has a taste of 5-8 year old whiskey and I doubt any whiskey was kept that long in M'Harry's time. But clearly (and we see this from Byrn) whiskey was kept at least a year or two in some cases and this would make a 50/50 corn and rye mash whiskey taste quite close I think to today's Rittenhouse or Pikesville which have a youngish taste. M'Harry's all corn whiskey probably was close to the Mellow Corn Mike has just reviewed. Wow.
In general the book is all-American, a no-nonsense savvy piece of work from a hands-on guy who knew his stuff. He makes an amusing knock for example at some scientists who never get their hands dirty making an actual fermentation. M'Harry was a man who had worked his way up, he states that specifically and it comes out in various other parts of the book. The language is old (in some cases) but the tone is quite modern, he was a smart guy, all business and (this comes through in many ways) with a well-developed ethical sense. There is no reference to Scotland, Germans or any of that stuff. He speaks as an American about a country that is fully formed and knows what it is about. His few references to foreign spirits (generally rum or gin or brandy) are to the effect of, "those drinks are okay but we can do better". He does in one section approve of foreign fermentation practice because he believes it results in cleaner ferments, continually he is concerned about ferments that might go sour but apart from that he shows no real interest in foreign liquors or the culture from which they (and Americans themselves, indirectly) sprang.
America in this book was a confident, self-sufficient country as early as 1809.
P.S. The part about rye being made to seem as brandy in fact is not that revealing (about whether bourbon was devised to resemble and compete in certain areas with cognac). He says add 1/4 to 1/3rd real brandy to rye whiskey and age it for a while and it will be an excellent brandy substitute. So nothing in the direction of aging all-cereal whiskey in new charred barrels and selling it to people as brandy...