I always had the idea that dragons weren't really "discovered" - I think they were kind of just a given presence in ancient times (like dogs, only a lot more dangerous to have around). But as the population decreased they fell out of general knowledge, and after a few centuries they became the stuff of legend.
As for the uses of dragon's blood, I think all the general theories have been covered. I only have one to add - an element in the Sorcerer's Stone. It's an idea I got when I saw the movie version of SS (I know that's not really what I should be going off of) and observed that the stone was a dark red, like blood. I figure if blood was used in its making then it would probably be the blood of some powerfully magical creature, like a dragon. However, if this use is true, then Dumbledore wouldn't have been the one to discover it; it would have had to have been Nicholas Flamel.
Dragon keepers like Charlie Weasley would of course have to do the usual jobs of making sure the muggles don't see the dragons, and keeping enough animals around for the dragons to eat. But I feel like they would have to protect the dragons as well. There must be dragon poachers in the wizarding world, people who hunt dragons for their magical parts like blood, not to mention their hide. Bill Weasley is said to have been wearing boots made of dragon hide when Harry first meets him in GoF (this always struck me as odd - how could Bill wear bits of dead dragon in the presence of Charlie, who clearly cares a lot about dragons? Wouldn't Charlie get mad at his brother?), and he can't be the only one. And if dragons do get killed, some might leave behind eggs or young dragons, which the keepers would probably have to raise in captivity for at least a few months, until they could survive on their own.
Dragons in Harry Potter are most certainly vicious and not of human intelligence. I guess they had to be that way in order to suit JK's purpose in the first challenge in GoF, but I've always liked stories in which dragons are considered wise, like Eragon, or even evilly intelligent, like The Hobbit. And personally, I think it would have been pretty exciting if Harry had had to get the golden egg from a dragon that could shout threats and insults inbetween breathing fire.
Some very nice ideas. 5 points.
I feel like I'm entering this after most the best points have been made. I have to agree with my fellow Slyths and say that dragons couldn't really be discovered. They were always around, but I'm sure it inspired awe and fear in most everyone that ran into them. I can see them rounding up shiny objects to place in their nests with their young, just like many of the medieval stories tell. That would have had many Muggles wondering what happened to their things. As man moved into their territories, the Wizards were forced to make sanctuaries for the protection of man a dragon. That is what led to the Romanian Dragon reserve.
I think much of the work done on the dragon reserve is to protect Muggles from the dragons as well as trying to help the dragons maintain territories and not crowd each other. I could see each breed being kept in different areas. When young are born, they would take them from the parents to try to tame them a little more then would be possible if left with the parents. This would also keep other adults from eating the young (I just see that as being one of the biggest problems... over crowding would get the dragons to attach other's nests). It is much like open range zoos. There is lots of danger and such for the keepers, but a necessary thing to keep dragons alive and Muggles safe.
I think Dumbledore slowly learned the nature of dragon blood. I have to agree with those that say he did research into history for starters. I also can see him finding out it was a great oven cleaner by accident. I actually see it more as a antidote then poison... mostly because of it's caustic nature. It would burn the poison out of the victim's system. This of course would have to be done slowly or it would burn a hole in the victim...
As for the other 10 uses, there are many possible choices, and with out doing the research or being told, it is hard to say. I think that it would be a very effective wart remover and/or cure to many fungi infections. I also think it was used to make the Sorcerer's Stone. Only Nicolaus Flamel could tell you that though... So I don't think it is part of the list actually taught to people. That would be the 13th use. Dumbledore didn't help make the Stone... it was make long before he was born. It might be part of what can turn elements into other elements. That is the main goal of Alchemy after all.
I agree with MQ in that the dragons of Harry Potter are very different from those that we see in modern fiction: they don’t seem to have a human-like intelligence or mystical quality. In fact, they just seem to be normal creatures that just happen to have wings and breathe fire and be very dangerous. If I had to pinpoint a type of dragon in mythology, Rowling’s dragons are very much like those of ancient Western legend, and less like those dragons of American and China or modern fantasy. Nor do the dragon’s overall personalities seem to vary from region to region in accordance with the legend of the area: a Chinese fireball eats humans, much like dragons do in Western fairytales, even though Oriental legend tends towards benevolent dragons.
Rowling diverges from the typical Western dragon, however, in that her dragons are not evil. They are extremely dangerous, but not dark at all: they are merely wild animals with an instinct to kill for survival and protect their young (as illustrated by the First Task in GOF).
Like others have said before me, I think that a dragon keeper is responsible not only for keeping dragons safe and healthy, but also to keep Muggles safe from them. After all, according to the Lexicon, there are at least three species of dragons that eat humans, if not more (as some species’ food isn’t mentioned, and the Norwegian Ridgeback eats “large mammals”, which could well include humans). Any type of contact between dragons and Muggles is sure to be deadly for both sides, because the dragons would want to eat and Muggles would want, in the very least, to protect their livestock.
What I’m interested in knowing is how endangered dragons are, or even if they are at all. Even though there are reservations around the globe, the Ministry seems to be rather lax about what they do with the dragons as long as they are kept away from Muggles. They use them for sport (the Triwizard tournament), security (Gringotts bank), and as magical ingredients (potions and wand cores) with what seems to be little regard for the dragon’s future. We don’t see any sort of restriction on slaughtering dragons for their horns, livers, skins, hearts, etc. A blind dragon was chained in front of a vault to protect it, its blindness vital because it seemed to make it fiercer (the goblins might have blinded it themselves, you never know). During the Triwizard Tournament, precious dragon eggs are trampled upon when a spell goes wrong…
If anything, I think that Charlie Weasley’s job would include censuses and dragon care not only to help the dragons, but to meet the Ministry’s ends. The measures taken seem to be keeping the Wizarding and Muggle populations safe, but no such luck for these magical creatures….
Excellent extension of points, and some great new thoughts. 5 points.