On this topic Mr. Spencer says : “And if already the loss from want of science is so frequent and so great, still greater and more frequent will it be to those who hereafter lack science. Just as fast as productive processes become more scientific, which competition will inevitably make them do, and just as fast as joint-stock undertakings spread, which they certainly will—so fast will scientific knowledge grow necessary to every one. * * * Had there been no teaching but such as is given in our public schools, England would be nOlv what it was in the feudal times..”These sentiments deserve to be written in letters of gold. At the present day knowledge increases so rapidly in every department, and is disseminated so generally by the periodical press, that t,he mechanic, the artizan, the manufacturm', and the dealer in stocks, who does not regularly read a paper devoted to science and the arts, soon becomes un ignorant man and labol's under nil the disadvantages ot his ignorance. As an essential part of every public man's life, unless he is a subscriber to a scientific periodical, he certainly is justly liable to the charge of ignorance and the want of common sensc, according to the teachings of. MI'. Herbert Spencer, for that is the vcry spirit of his teachings. —-., —- PATENT LAWS of the United States, together with an epitome of the Patent Laws of foreign countries, is just issued and for sale at this office. It contains over 100 pages of useful information upon almost every question that relates to patents, and will be found of much service to all who are interested in such matters. Single copies by mail, 2,; cents: at the countcr, 20 cents, Inclose stamps or change, and address MUNN &Co., office of the SCIENTIFIC AMERICAN. I .-—