"Inertia has a sway as absolute in natural philosophy over moving bodies as over those at rest. It therefore does not retard motion or change, but is as frequently active in continuing that state as in opposing it. Now, is this the case with mental inertia?" These passages from Faraday's early lectures serve to show us not only how he was attaining the art of expressing himself clearly, but how thoroughly he went into a subject on which he had once entered. It is not possible to follow in detail the work on which Faraday was engaged. We have seen him learning assiduously, and essaying to teach in the friendly circle of the Philosophical Society. His work during the next few years continued on very similar lines to those which we have been regarding. Year by year, about this time, his scientific writing increased--his work was increasing, his friends were increasing--he was beginning to be "somebody," though as yet but in a small world. He had commenced a correspondence with Professor G. de la Rive--the gentleman who at Geneva had been so struck by him when he was acting as Davy's travelling factotum--a correspondence which on the death of De la Rive was continued with his son, Professor Auguste de la Rive. In 1821 Faraday married. Before, however, we treat of this important step in his life, let us glance at the journal which he kept of a walking tour he took in Wales during the summer of 1819. This journal gives us further evidence of the genuine enjoyment which he found in scenery and nature in her wilder and more impressive aspects; it also gives further evidence of his simple yet direct way of describing things, of that true descriptive power of which his Continental journal was often a good illustration. At five o'clock in the morning of July 10th, he mounted the top of the _Regulator_ coach at the White Horse Cellar, Piccadilly, and at ten o'clock of the same evening was set down at Bristol. Not at all a bad coach-ride for one day's journey. He afterwards visited Cardiff, and went over the Dowlais Ironworks at Merthyr; thence he and his companion wandered about at their own sweet will, unconfined by any artificial circumstances. They walked in that manner which adds so great a charm to a walking tour, never knowing one day whither they should bend their way on the next. The following is a delightful bit descriptive of a visit to the Fall of Scwd-yv-hên-rhyd, or Glentaree, formed by the descent of the River Hên-rhyd.