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 electrical conductors is avoided, and that the capital invested is smaller than is required for gas-works. Heretofore the difficulty experienced by electricians has been to divide the light without weakening in too large a degree its power. Should the system of Messrs. Molera and Cebrian prove a practical success, it may be economically used in lighting not only private residences and public institutions, but even whole cities."

Color-Blindness of Seamen.—An article on color-blindness, in a late number of the "English Mechanic," quotes some very important facts from the records of the British Board of Trade, derived from examinations of seamen applying for "mate's" or "master's" certificates, concerning their ability to distinguish colors. We select a few from the many instances of colorblindness detected by these examinations. One seaman, a candidate for a second master's certificate, described green glass as "dark red"; in another case a green card was called "yellow"; and a man who had been over eighteen years at sea was reported as quite unable to distinguish any of the colors. Another who had been more than seven years at sea described the red glass by daylight as "green," the dark green as "red," and the yellow as "red"; while by gaslight he named the light blue "green," the dark green "red," and the yellow "red." This appears to be a case of Daltonism, or incapability of perceiving the red end of the spectrum. There are several similar instances which differ only in details; but perhaps the most interesting case is that of a candidate for a second mate's certificate who had served nearly five years at sea—a case that ought to have been sent to a court of appeal. By daylight he described the red card as "green," the yellow and green glasses "red," and the red glass as "dark green." By artificial light he called the yellow and green glasses "red," and the white glass "dark green." This man obtained a certificate from the London Ophthalmic Hospital testifying that he was not color-blind, but on reëxamination he still described dark green as "red," light green as "neutral," and yellow as "red" by artificial light, while by daylight he called the green glasses "red" once and "yellow" once. This last difference may have been caused by the manner in which the question was put, and ignorance of the names of colors. In view of these facts, the query suggests itself, may not the recent dreadful accident to the steamer Champion have been due to the inability of the lookout to distinguish the lights on the other ship, which was discovered only when near enough to take in her general outline?

Apprentice-Schools in France.—This is the title of a highly suggestive paper on the subject of science teaching in the public schools, read by Professor S. P. Thompson at the last meeting of the British Association. As the subject is daily acquiring new importance in this country, we present a pretty full abstract of the paper as it appeared in "Nature." The problem to be solved, in the author's opinion, is, how to give that technical training and scientific knowledge to artisan children which their occupation demanded, without detaining them so long at their schooling as to create a distaste for manual labor. There were four solutions of the problem, all of which had been tried, and illustrations of which could be seen in Paris. They were: 1. Send the children to work in the factory or workshop at an earlier age, making it obligatory all through their apprenticeship that they should have every day a certain number of hours' schooling in a school in the workshop or attached to it; 2. Keep the children at school as long as their education was unfinished, but set up a workshop in the school, where they should pass a certain amount of time every day so as to gain at least an aptitude for manual labor; 3. Organize a school and a workshop side by side and coöordinate the hours given to study with an equal number of hours devoted to systematic manual labor; and, 4. Send the children half the day to the existing schools, and the other half to work half-time in the workshop or factory. Schools of the first type had existed in France for nearly thirty years, and at the close of 1878 there were no fewer than 237 schools of this character. So far as he was aware, there was only one school of the second type—the Ecole communale d'Apprentis, in the Rue Tournefort, Paris. The peculiarity of this school was that workshop training was being given to lads who had not yet completed a course