In working, also, he was very careful not to employ more force than was wanted to produce the effect. When his experiments were finished and put away, he would leave the laboratory, and think further about them upstairs. This orderliness and this economy of means he not only practised himself, but he expected them also to be followed by any who worked with him; and it is from conversation with these that I have been enabled to give this sketch of his manner of working.[19] This exactness was also apparent in the accounts he kept with the Royal Institution and Trinity House, in which he entered every little item of expenditure with the greatest minuteness of detail. It was through this lifelong series of experiments that Faraday won his knowledge and mastered the forces of nature. The rare ingenuity of his mind was ably seconded by his manipulative skill, while the quickness of his perceptions was equalled by the calm rapidity of his movements. He had indeed a passion for experimenting. This peeps out in the preface to the second edition of his "Chemical Manipulation," where he writes, "Being intended especially as a book of instruction, no attempts were made to render it pleasing, otherwise than by rendering it effectual; for I concluded that, if the work taught clearly what it was intended to inculcate, the high interest always belonging to a well-made or successful experiment would be abundantly sufficient to give it all the requisite charms, and more than enough to make it valuable in the eyes of those for whom it was designed." He could scarcely pass a gold leaf electrometer without causing the leaves to diverge by a sudden flick from his silk handkerchief. I recollect, too, his meeting me at the entrance to the lecture theatre at Jermyn Street, when Lyon Playfair was to give the first, or one of the first lectures ever delivered in the building. "Let us go up here," said he, leading me far away from the central table. I asked him why he chose such an out-of-the-way place. "Oh," he replied, "we shall be able here to find out what are the acoustic qualities of the room." The simplicity of the means with which he made his experiments was often astonishing, and was indeed one of the manifestations of his genius.