"I presume that may be the case, and it would help to explain why magic itself has been outwardly discredited as a science—which is the point I'm getting at.
"Suppose the basic formulas of physics—such as Newton's three laws of motion—had changed several times in the last few thousand years. The discovery of any physical laws at any time would have been vastly more difficult. The same experiments would give different results in different ages. But that is the case with magic, and explains why magic has been periodically discredited and has become repugnant to the rational mind. It's like what old Carr was saying about the run of the cards at bridge. After a few shuffles of a multitude of cosmic factors, the laws of magic change. A sharp eye can spot the changes, but continual experimentation, of the trial-and-error sort, is necessary to keep the crude practical formulas of magic in anything like working order, especially since the basic formulas and the master-formulas have never been discovered.
"Take a concrete example—the formula I used Sunday night. It shows signs of recent revision. For instance, what did the original, unrevised formula have in place of the phonograph needle?"
"A willow whistle of a certain shape, which had been blown only once," the voice told him.
"And the platinum or iridium?"
"The original formula mentioned silver, but a heavier metal serves better. Lead, however, proved altogether ineffective. I tried it once. It was apparently too unlike silver in other respects."
"Precisely. Trial-and-error experimentation. I have a modern substitute for the flannel wrapping which may prove more effective. Moreover, in the absence of thorough investigation, we cannot be sure that all the ingredients of a magic formula are essential in making it work. A comparison of the magic formulas of different countries and peoples would be helpful in this respect. It would show which ingredients are common to all formulas and therefore presumably essential, and which are not essential. I have in mind a method for making such a comparison."
There was a discreet knock at the door. Norman spoke a few words, and the figure drew down its veil and turned toward the window, as if staring stolidly at the passing fields. Then he opened the door.
It was lunch, as long in coming as breakfast had been. And there was a new face—coffee-colored instead of ebony. Evidently the first waiter, who had shown growing nervousness in his previous trips to the compartment, had decided to sacrifice the tip and send someone else.