Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 4, 1802).djvu/473

Rh continued for a longer time, and with a moderate degree of heat: thus, the gummy extract will become nearly colourless; but, if volatile alkali be used, it will be necessary to substitute iron vessels for those made of copper.

Lord D.'s gum has been found to answer every purpose for which it was designed: as its preparation is not only cheaper, and will produce a considerable saving of money annually sent to Senegal, but will also afford employment to numerous women, children, and others, in collecting, as well as in preparing, the lichens, it promises to be a national benefit.  LOCK.—In June, 1801, a patent was granted to Mr., for his invention of locks or fastenings adapted for general use, on a new and improved construction.—The external form of the locks, thus manufactured, corresponds with those in common use: internally, however, an orbicular bolt is substituted for a rectilineal one, the security of which is increased by an inside tumbler that is fastened by a flat spring bolt. The whole manufacture of this lock is remarkable for its simplicity and ingenuity, with which it combines the important advantage of security; so that this contrivance justly merits the preference.  LOGIC, is the art of thinking and reasoning with judgment and propriety: or, it may be defined to be the history of the human mind; because it traces the progress of knowledge from the first and most simple conceptions, through all their various combinations, gradations, and the inferences that are drawn from a comparison of ideas.

Logic is, doubtless, one of the most important sciences that can be impressed on the young mind; inasmuch as it unfolds the nature of the faculty of reflection, while it displays the proper manner in which the mental powers are to be exercised, in the pursuit of truth and knowledge. Farther, it cautions us against those errors and mistakes to which we are liable in consequence of inattention; while it teaches us to discriminate between real and apparent truth; being thus admirably calculated for the investigation of interesting subjects, both of literature and morality; as it enables parties to detect the fallacy of. We could with pleasure point out other essential advantages, resulting from the art of thinking; and, though a reference has been made from our first volume to this article, for a farther investigation of error in arguments, yet, as such discussion would lead us into too wide a field of speculation, we refer the reader to the following excellent works, in which the first principles of reasoning are clearly developed, and the juvenile mind is taught to distinguish between truth and falsehood.—1. "Elements of Logic," by Prof., of Aberdeen, 8vo.; 2. Dr. 's "Chart and Scale of Truth, by which to find the Cause of Error," &c. 2 vols. 8vo.; and 3. Mr. 's "Essentials of Logic," &c. 12mo. 2d edit. pp. 223, 1796.