Ishmael notes that the Tranque sperm whale’s skeleton measured about 72 feet in length, and that this skeleton did not really do justice to the actual bulk of the whale, since a layer of blubber and skin would cover this skeleton. Ishmael states that, in some sense, the skeleton shows only the shadow of the greatness and sublimity of the whale itself. And once again returning to the topic of the whale’s spine, Ishmael says that the largest whale vertebra was about three feet wide—the shortest, so small that it was stolen by some of the priest’s children and used as a “toy.”
Ishmael does precisely measure the whale skeleton, and what is amazing is that he then insists that the whale maintains its mystery because it is that which he can't measure—the whale in its blubber and skin that is the true whale. As always, Ishmael's attempts to define or understand the whale leaves him understanding just a "shadow" of the whale.