From outside it was simply an ordinary looking London pub, a place you'd have to be guided to more than once before you memorized it's location, somewhere between Fleet Street and the Embankment. But, if by chance, an insider led you to the White Hart on a Wednesday night, you would have found yourself in the midst of a select gathering or writers, editors, scientists and interested laymandrinking, swapping odd bits of information, and, like as not, listening to Harry Purvis' memorable stories. A scientist by profession, Harry Purvis has had or heard about some of the most astonishing experienceslike the story of the carnivorous orchid that was used in a murder plot, or the one about the military computer that was converted to pacifism. There's Silence Please, involving a spurned lover and a device that was supposed to destroy sound; and Big Game Hunt, in which an ambitious researcher becomes so wrapped up in his latest projectcontrolling animal behavior with electrical impul