“As though knowing could be any satisfaction to a man!

“But I went to work — like a slave. And I had hardly worked and thought about the matter six months before light came through one of the meshes suddenly — blindingly! I found a general principle of pigments and refraction — a formula, a geometrical expression involving four dimensions. Fools, common men, even common mathematicians, do not know anything of what some general expression may mean to the student of molecular physics. In the books — the books that tramp has hidden — there are marvels, miracles! But this was not a method, it was an idea, that might lead to a method by which it would be possible, without changing any other property of matter — except, in some instances colours — to lower the refractive index of a substance, solid or liquid, to that of air — so far as all practical purposes are concerned.”

“Phew!” said Kemp. “That’s odd! But still I don’t see quite ... I can understand that thereby you could spoil a valuable stone, but personal invisibility is a far cry.”

“Precisely,” said Griffin. “But consider, visibility depends on the action of the visible bodies on light. Either a body absorbs light, or it reflects or refracts refracts it, or does all these things. If it neither reflects nor refracts nor absorbs light, it cannot of itself be visible. You see an opaque red box, for instance, because the colour absorbs some of the light and reflects the rest, all the red part of the light, to you. If it did not absorb any particular part of the light, but reflected it all, then it would be a shining white box. Silver! A diamond box would neither absorb much of the light nor reflect much from the general surface, but just here and there where the surfaces were favourable the light would be reflected and refracted, so that you would get a brilliant appearance of flashing reflections and translucencies — a sort of skeleton of light. A glass box would not be so brilliant, not so clearly visible, as a diamond box, because there would be less refraction and reflection. See that? From certain points of view you would see quite clearly through it. Some kinds of glass would be more visible than others, a box of flint glass would be brighter than a box of ordinary window glass. A box of very thin common glass would be hard to see in a bad light, because it would would absorb hardly any light and refract and reflect very little. And if you put a sheet of common white glass in water, still more if you put it in some denser liquid than water, it would vanish almost altogether, because light passing from water to glass is only slightly refracted or reflected or indeed affected in any way. It is almost as invisible as a jet of coal gas or hydrogen is in air. And for precisely the same reason!”

“Yes,” said Kemp, “that is pretty plain sailing.”

“And here is another fact you will know to be true. If a sheet of glass is smashed, Kemp, and beaten into a powder, it becomes much more visible while it is in the air; it becomes at last an opaque white powder. This is because the powdering multiplies the surfaces of the glass at which refraction and reflection occur. In the sheet of glass there are only two surfaces; in the powder the light is reflected or refracted by each grain it passes through, and very little gets right through the powder. But if the white powdered glass is put into water, it forthwith vanishes. The powdered glass and water have much the same refractive index; that is, the light undergoes very little refraction or reflection in passing from one to the other.

We brought up just where the anchor was in the chart, about a third of a mile from each shore, the mainland on one side and Skeleton Island on the other. The bottom was clean sand. The plunge of our anchor sent up clouds of birds wheeling and crying over the woods, but in less than a minute they were down again and all was once more silent.

The place was entirely land–locked, buried in woods, the trees coming right down to high–water mark, the shores mostly flat, and the hilltops standing round at a distance in a sort of amphitheatre, one here, one there. Two little rivers, or rather two swamps, emptied out into this pond, as you might call it; and the foliage round that part of the shore had a kind of poisonous brightness. From the ship we could see nothing of the house or stockade, for they were quite buried among trees; and if it had not been for the chart on the companion, we might have been the first that had ever anchored there since the island arose out of the seas.

There was not a breath of air moving, nor a sound but that of the surf booming half a mile away along the beaches and against the rocks outside. A peculiar stagnant smell hung over the anchorage—a smell of sodden leaves and rotting tree trunks. I observed the doctor sniffing and sniffing, like someone tasting a bad egg.

“I don’t know about treasure,” he said, “but I’ll stake my wig there’s fever here.”

If the conduct of the men had been alarming in the boat, it became truly threatening when they had come aboard. They lay about the deck growling together in talk. The slightest order was received with a black look and grudgingly and carelessly obeyed. Even the honest hands must have caught the infection, for there was not one man aboard to mend another. Mutiny, it was plain, hung over us like a thunder–cloud.

And it was not only we of the cabin party who perceived the danger. Long John was hard at work going from group to group, spending himself in good advice, and as for example no man could have shown a better. He fairly outstripped himself in willingness and civility; he was all smiles to everyone. If an order were given, John would be on his crutch in an instant, with the cheeriest “Aye, aye, sir!” in the world; and when there was nothing else to do, he kept up one song after another, as if to conceal the discontent of the rest.

Of all the gloomy features of that gloomy afternoon, this obvious anxiety on the part of Long John appeared the worst.

We held a council in the cabin.

“Sir,” said the captain, “if I risk another order, the whole ship’ll come about our ears by the run. You see, sir, here it is. I get a rough answer, do I not? Well, if I speak back, pikes will be going in two shakes; if I don’t, Silver will see there’s something under that, and the game’s up. Now, we’ve only one man to rely on.”

“And who is that?” asked the squire.

“Silver, sir,” returned the captain; “he’s as anxious as you and I to smother things up. This is a tiff; he’d soon talk ’em out of it if he had the chance, and what I propose to do is to give him the chance. Let’s allow the men an afternoon ashore. If they all go, why we’ll fight the ship. If they none of them go, well then, we hold the cabin, and God defend the right. If some go, you mark my words, sir, Silver’ll bring ’em aboard again as mild as lambs.”