the end of this period he became for a time Captain Moorsum's engineering secretary, and during this time he devised the little instrument which he called the velocimeter, and described in the Civil Engineer's Journal. It was for the purpose of calculating, by mechanical means, the speeds of locomotive engines from given fractional distances and times, which otherwise required much trouble in estimating the velocity. Then followed a period of some six months occupied in out-door works, partly in superintending the completion of constructions, and partly in testing the performances of engines.
During this period he was led, by collecting fossils, into the study of geology, and read Sir Charles Lyell's "Principles," then recently published. The noteworthy fact respecting this is, that in it the doctrine of Lamarck respecting the development of species is there set forth, combated and rejected. Mr. Spencer cannot say whether he was before familiar with this doctrine, but he remembers that Lyell's arguments failed to disprove it to him, and he became, thereafter, a firm believer in the general idea that all organized beings had arisen by development (1839). He had so profound a belief in natural causation, in general so strong a tendency to see a unity of processes in things, that an hypothesis of this kind, which suggested that the genesis of organisms had arisen from physical actions, was one that he was prepared to accept as congruous with the system of things known by experience. Such a notion as that of miracle, utterly inharmonious with the ideas of cause and law and order which had become ingrained in him, was inadmissible, and hence the only alternative view presented itself to his mind as obviously necessary. Nothing ever afterward shook this belief. There naturally went along with this a gradual dropping of the current theology, although Mr. Spencer cannot say when it began or when it ended. The conception of the natural genesis of things gradually replaced the conception of the supernatural genesis, and belief in the prevailing creed gradually faded away.
In April, 1841, having declined the offer of an engineering appointment, Mr. Spencer returned home, intending to carry further his mathematical studies. Very little came of this intention, however, and some two years were spent at home in a miscellaneous and seemingly futile manner. Botany occupied his attention for some months. He made a botanical press and an herbarium. He practised drawing to some extent, and made pencil-portraits of various friends. Phrenology, of which he did not at that time see the fallacies, occupied some attention. All the time, however, he had in progress one or other scheme of invention. Improvements in watch-making, machines for making type by compression of the metal instead of casting, a printing-press of a new form, the application of the electrotype for engraving, afterward known as the glyptograph, occupied his attention. The great flood in Derby, in 1842, caused by the sudden overflow of a tributary of the Derwent, having occurred, Mr. Spencer wrote
