These fish, it seems, have strong bony palates and throat-teeth for crushing shells and crabs, and make this wonderful noise simply by grinding their teeth together.
I vouch for nothing, save that I heard this strange humming more than once.

As for the cause of it, I can only say, as was said of yore, that 'I hold it for rashness to determine aught amid such fertility of Nature's wonders.' One afternoon we made an attempt on the other Guacharo cave, which lies in the cliff on the landward side of the Monos Boca.

But, alas! the wind had chopped a little to the northward; a swell was rolling in through the Boca; and when we got within twenty yards of the low-browed arch our crew lay on their oars and held a consultation, of which there could but be one result.

They being white gentlemen, and not Negroes, could trust themselves and each other, and were ready, as I know well, to 'dare all that became a man.' But every now and then a swell rolled in high enough to have cracked our sculls against the top, and out again deep enough to have staved the boat against the rocks.

If we went to wreck, the current was setting strongly out to sea; and the Boca was haunted by sharks, and (according to the late Colonel Hamilton Smith) by a worse monster still, namely, the giant ray, {111a} which goes by the name of devil-fish on the Carolina shores.