P OP ULAR MIS CELL ANY. 



141 



The English Mile. M. Faye lias ex- 

 plained 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 geogra- 

 phers deduced their mile from Ptolemy, and 

 Ptolemy refers to Eratosthenes. Eratosthe- 

 nes measured the arc of the meridian on the 

 basis of the distance between Syene and Al- 

 exandria, in Egypt, which gave seven hun- 

 dred stadia to the degree. Ptolemy says 

 that he verified the measurements of Era- 

 tosthenes, 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. Eratos- 

 thenes 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 ge- 

 ographers, in making their calculation, be- 

 lieved that Ptolemy had used still another 

 foot, the Greek foot, which is one and a 

 half hundredths longer than ours, but short- 

 er 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 Exhibi- 

 tion. The International Exhibition of Elec- 

 tricity at Paris was satisfactorily opened 

 August 11th, though the preparations still 

 lacked something of being completed. The 

 exhibition represents, in two distinct divi- 

 sions first, appliances of electric lighting ; 

 and, second, the other applications of elec- 

 tricity. 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-IIungary, Russia, 

 Sweden and Norway, Italy, Spain, Switzer- 



land, Holland, and Denmark. Japan ex- 

 hibits 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, sur- 

 rounded by a basin, in which a boat pro- 

 pelled 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 sun- 

 lamp, 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, fur- 

 nished 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 Theatre Francais. Other rooms are de- 

 voted to electropathy, electric photography, 

 testing instruments, a retrospective exhibi- 

 tion 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 trans- 

 mission of letters and telegrams traverses 

 the south gallery. 



Propagating Sponges by Cnttings. The 



Austrian Government has made some suc- 

 cessful 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 " Transac- 

 tions of the Zoological-Botanical Society of 

 Vienna." The most suitable season for un- 

 dertaking 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- 



