APPENDIX.
Under this head I place some articles which could not be embodied in this work; but which it may nevertheless be expedient to place within the reach of certain readers. Among the articles referred to is the theory of electricity, which I first published in 1848, and which has been approved by the spirit of Franklin, and, in obedience to his advice, inserted in this volume. Unfortunately, there are but few persons sufficiently acquainted with the phenomena which form its basis, and the technical language employed by professed electricians, to find it agreeable to study the subject in question; but they may qualify themselves to do so by studying the elementary works on this branch of science.