“Learn of the little Nautilus to sail,” and some of us may be acquainted with those graceful verses of James Montgomery, in his “Pelican Island:”-- “Light as a flake of foam upon the wind, Keel upward, from the deep emerged a shell, Shaped like the moon ere half her horn is filled. Fraught with young life it righted as it rose, And moved at will along the yielding water. The native pilot of this little bark Put out a tier of oars on either side, Spread to the wafting breeze a two-fold sail, And mounted up and glided down the billow In happy freedom, pleased to feel the air, And wander in the luxury of light. * * * * * It closed, sank, dwindled to a point, then nothing, While the last bubble crowned the dimpling eddy Through which mine eye still giddily pursued it.” So deeply ingrained is the poetical notion of the sailing powers attributed to the nautilus, that many people are quite incredulous when they are told that there is just as much likelihood of seeing a mermaid curl her hair as of witnessing a nautilus under sail. How the creature in question does propel itself will be described in the course of the present chapter; and the reader will see that although one parallel between Nature and Art in the nautilus does not exist, there are several others which until later days have not even been suspected. It is, therefore, partially true that science does destroy romance. But, though she destroys, she creates, and she gives infinitely more than she takes away, as is shown in the many late discoveries which have transformed the whole system of civilised life. Sometimes, as in the present instance, she discovers one analogy while destroying another, and though she shatters the legend of the sailing nautilus, she produces a marine animal which really does sail, and does not appear to be able to do anything else. This is the VELELLA, a figure of which, taken from a specimen in my collection, is given in the illustration, and drawn of the natural size. It is one of that vast army of marine creatures known familiarly by the name of “jelly-fishes,” just as lobsters, crabs, shrimps, oysters, whelks, periwinkles, and the like, are lumped together under the title of “shell-fish.” As a rule, these creatures are soft, gelatinous, and, in fact, are very little more than sea-water entangled in the finest imaginable mesh-work of animal matter; so fine, indeed, that scarcely any definite organs can be discovered. The Velella, however, is remarkable for having a sort of skeleton, if it may be so called, consisting of two very thin and horny plates, disposed, as shown in the illustration, so as to form an exact imitation (or perhaps I should say a precursor) of a raft propelled by a sail. Indeed, the Latin name Velella signifies a little sail. [Illustration: VELELLA (NATURAL SIZE).] [Illustration: SAILING RAFT.]