The English Mile.—M. Faye has explained why it takes sixty-nine and a half English miles to make a degree instead of sixty, as was probably intended when the mile was established. The English geographers deduced their mile from Ptolemy, and Ptolemy refers to Eratosthenes. Eratosthenes measured the arc of the meridian on the basis of the distance between Syene and Alexandria, in Egypt, which gave seven hundred stadia to the degree. Ptolemy says that he verified the measurements of Eratosthenes, and found the same result, which he gives, however, as five hundred stadia to the degree. The discrepancy arises from a change which took place in the standard of the foot—of which six hundred went to the stadium—during the four hundred years between Eratosthenes and Ptolemy. Eratosthenes used the ancient Egyptian foot, which is shorter than ours, while Ptolemy used the Phileterian foot, which is longer than ours. Making allowance for this difference, the two measurements agree. The English geographers, in making their calculation, believed that Ptolemy had used still another foot, the Greek foot, which is one and a half hundredths longer than ours, but shorter than the one he did actually use. If the English geographers of the sixteenth century had strained this valuation ever so little, and had carried it to five one-hundredths, they would have found 630 English feet for the stadium, which they believed to be 600 Greek feet, and these 630 feet, or 210 yards, multiplied by 500, would give them 105,000 yards for the degree, and exactly 1,760 yards for the mile.
The International Electrical Exhibition.—The International Exhibition of Electricity at Paris was satisfactorily opened August 11th, though the preparations still lacked something of being completed. The exhibition represents, in two distinct divisions—first, appliances of electric lighting; and, second, the other applications of electricity. In the second division, England and Germany have the first places on the left of the entrance, with one thousand square metres of space each; after them follow, in order of the size of their exhibits, Belgium, America, Austro-Hungary, Russia, Sweden and Norway, Italy, Spain, Switzerland, Holland, and Denmark. Japan exhibits a table of porcelain vases and jars of lacquered stuff for insulators. The French exhibits are on the right, and in the center of the palace is an electric lighthouse, surrounded by a basin, in which a boat propelled by electricity moves around. The twenty-eight rooms of the first floor are each lighted by a different system of electric lighting. One room, lighted by the sunlamp, contains pictures and works of art to show the application of electricity to the lighting of museums. Another room is a completely furnished theatre, lighted by the Werdemann system. Two other rooms, furnished as a suite, contain the applications of electricity to domestic and social life. In the next rooms electrical playthings are collected, and in the rooms adjoining are telephones, by means of which visitors are brought within hearing of the Opera and the Théâtre Français. Other rooms are devoted to electropathy, electric photography, testing instruments, a retrospective exhibition of historical apparatus, and, lastly, Mr. Edison's inventions. Visitors are brought from the Place de la Concorde to the door of the exhibition on an electric tramway, and a little electric railway for the transmission of letters and telegrams traverses the south gallery.
Propagating Sponges by Cuttings.—The Austrian Government has made some successful experiments in the propagation of sponges from cuttings in the Adriatic Sea, accounts of which have been published by Dr. Emil von Marenzeller, in the "Transactions of the Zoölogical-Botanical Society of Vienna." The most suitable season for undertaking the propagation is the winter; for, although the growth of the sponges and the healing of the cut surfaces takes place more slowly then than in the summer, the sponges are much less liable to be spoiled by putrefaction. The suitableness of a spot for the cultivation is surely indicated by the freshness and liveliness of the marine algae growing in it. It demands a bay sheltered from strong waves and currents, but not quite still, a rocky bottom, clothed with living alga?, and a moderate ebb and flow of the tide. In all cases the neighborhood of the mouths of brooks, rivers, and sub-
