It is not, in truth, a just reproach to unsuspecting men, that they have not seen what they never imagined the presence of. It would scarcely have been so, had they failed to see in a given place what they were told was likely to be found. Many of our readers are familiar with the existence of black lines in the solar spectrum; many may have seen them, and justly wondered. Some may even recollect, when, years ago, Frauenhofer first announced their existence, how opticians everywhere mounted their most homogeneous prisms, and gazed at the spectrum eager to see them, and how many looked in vain. Of course, the failure was ascribed to the imperfection of their prisms, and not to their own defective skill. One philosopher we remember, then already distinguished, and whom now all delight to honour, of whom it was told that having obtained one of the beautifully perfect prisms of Frauenhofer’s own manufacture, he was still unable to see the lines; but that another who had seen them came to his aid, instructed him how to look, and in an instant he not only clearly saw them, but exclaimed with wonder at his own blindness. Such were our own sensations also when first we saw them. Was it, then, a reproach to Sir Isaac Newton and his successors that these lines escaped them? The same reproach might be made to the predecessors of almost every discoverer in every walk of modern science. Many before him probably had looked from the same spot, with similar advantages for seeing, and had not seen. But they had gazed without any special object or previous instruction, and they had failed to discern what another coming after them, prepared to look for it, and knowing what it was like, and where likely to be, would have at once descried. Hence the discovery of most of the rich mines in past times was the result of some unlooked-for accident happening generally to naturally-observant but ignorant men. Thus Jacob says of the mines in the Hartz— “There are various conflicting opinions among the learned in antiquities respecting the discovery of the mineral wealth of the Hartz. The most probable accounts fix it in the tenth century; and the tradition is, that a hunter of the name of Ramm, when engaged in the chase, had fastened his horse to a tree, who, by pawing with his feet, had scraped away the soil, and thereby discovered some minerals; that specimens of them were sent to the Emperor Otho, to whom all minerals, as regalities of the Empire, belonged, and who sent expert miners to examine the district, from Franconia.”—(JACOB, i. p. 254.) And again of the mines of Saxony—