It is, however, necessary, in the first place, clearly to understand the difference between the discovery of Vulcan, and that of the small planets, which are now so numerous that the announcement of a new one has ceased to be a matter of interest. The discovery of Vulcan ranks with that of Neptune. It is not, however, likely to excite such popular interest, as there are no contending national claims. There is no Adams in this case to dispute the claim with Leverrier. It has, therefore, simply the interest of one of the greatest triumphs of the human intellect. In the case of the asteroids, the discovery implies no prophetic vision. Let a man, with proper instruments and charts, explore a certain region of the heavens, and there is a probability, almost amounting to certainty, that he will, within a few months, discover a new one, though he have few or no scientific accomplishments. From experience, it has been found that, in a certain zone, these asteroids abound, and, from the rate of discovery in the past, we naturally infer the rate of the future. This case is wholly different from that of Neptune and Vulcan, where the existence of the planets was predicted on a-priori grounds. The matter may be illustrated by the discovery of gold in Australia. The digger buys a claim on the banks of a river, sinks a shaft, and is fortunate enough to discover some nuggets. But there is no scientific merit in this. He was only led by an instinct, which is as strong in the inferior animals as in man. He
