BY those accustomed to the hopeless confusion of the Greywacké of the earlier geologists, the publication of Murchison's grand work on the “Silurian System” was hailed with feelings of the most profound relief and satisfaction. His clear and brilliant presentation of the physical and palæontological proofs of an orderly sequence among the Palæozoic Rocks below the Old Red Sandstone, as originally set forth in all their force and harmony in his magnificent volumes, naturally astonished and dazzled the majority of his scientific contemporaries, and secured for his nomenclature of these ancient deposits an almost universal acceptance. His subsequent abuse of this advantage to strengthen and consolidate his own system at the expense of that of his equally - illustrious co-worker—the less fortunate but more cautious Sedgwick —was a gallant but unscrupulous defence of this original nomenclature, which by that time he must have felt himself almost powerless to disturb. His later extension downward of the limits of his system, till it embraced all the rocks between the supposed Azoics and the Old Red Sandstone—though, in a measure, forced upon him from without—ought perhaps to be regarded in part as a very natural return to the ideas of his early teachers, who had always held the practical unitly of the rocks of the Transitionalperiod. In this wey, however, Murchison unwittingly destroyed many of the most beneficial results of his won labours; in a sense, spending his old age in the attempted re-erection of the very edifice it hed been the pride of his manhood to destroy—the early years of his scientific career being devoted to the worthy task of proving the marvellous variety of the Lower Palæozoics; his later years to demonstrating their integrity, unity, and indivisibility.