That Pteraspis and shark were his cousins, great-uncles, or grandfathers, in no way troubled him, but that either or both of them should be older than evolution itself seemed to him perplexing; nor could he at all simplify the problem by taking the sudden back-somersault into Quincy Bay in search of the fascinating creature he had called a horseshoe, whose huge dome of shell and sharp spur of tail had so alarmed him as a child. In Siluria, he understood, Sir Roderick Murchison called the horseshoe a Limulus, which helped nothing. Neither in the Limulus nor in the Terebratula, nor in the Cestracion Philippi, any more than in the Pteraspis, could one conceive an ancestor, but, if one must, the choice mattered little. Cousinship had limits but no one knew enough to fix them. When the vertebrate vanished in Siluria, it disappeared instantly and forever. Neither vertebra nor scale nor print reappeared, nor any trace of ascent or descent to a lower type. The vertebrate began in the Ludlow shale, as complete as Adams himself--in some respects more so--at the top of the column of organic evolution: and geology offered no sort of proof that he had ever been anything else. Ponder over it as he might, Adams could see nothing in the theory of Sir Charles but pure inference, precisely like the inference of Paley, that, if one found a watch, one inferred a maker. He could detect no more evolution in life since the Pteraspis than he could detect it in architecture since the Abbey. All he could prove was change. Coal-power alone asserted evolution--of power--and only by violence could be forced to assert selection of type. All this seemed trivial to the true Darwinian, and to Sir Charles it was mere defect in the geological record. Sir Charles labored only to heap up the evidences of evolution; to cumulate them till the mass became irresistible. With that purpose, Adams gladly studied and tried to help Sir Charles, but, behind the lesson of the day, he was conscious that, in geology as in theology, he could prove only Evolution that did not evolve; Uniformity that was not uniform; and Selection that did not select. To other Darwinians--except Darwin--Natural Selection seemed a dogma to be put in the place of the Athanasian creed; it was a form of religious hope; a promise of ultimate perfection. Adams wished no better; he warmly sympathized in the object; but when he came to ask himself what he truly thought, he felt that he had no Faith; that whenever the next new hobby should be brought out, he should surely drop off from Darwinism like a monkey from a perch; that the idea of one Form, Law, Order, or Sequence had no more value for him than the idea of none; that what he valued most was Motion, and that what attracted his mind was Change.