SCIENCE, INVENTION, DISCOVERY. 



303 



to make a crown of pure gold, had fraudu- 

 lently mixed with the metal. The solution of 

 the problem had suggested itself to him as he 

 was entering the bath, and he is reported to 

 have been so overjoyed as to hasten home with- 

 out waiting to dress, exclaiming, "I have 

 found it ! I have found it ! " Among the 

 numerous inventions ascribed to Archimedes is 

 that of the endless screw, and the cochlea, or 

 water-screw, in which the water is made in a 

 manner to ascend by its own gravity. 



Atlantic Cables In July, 1866, the 

 first permanent Atlantic cable was laid from 

 Valentia Bay, Ireland, to Trinity Bay, N. F., 

 and in September of the same year a cable 

 which had been lost in 1865 was recovered 

 and its laying completed, thus giving two lines 

 between the two points. These lines were 

 known as the Anglo-American Cable, and 

 were managed by a company of the same 

 name. The French Atlantic Telegraph Com- 

 pany was formed in 1868, and it laid a line 

 from Brest, France, to Roxbury, Mass., the 

 following year. In the summer of 1873 the 

 fourth Atlantic telegraph cable was laid from 

 Valentia, Ireland, to Heart's Content, Trinity 

 Bay, N. F., and the Brazilian telegraph cable 

 was laid from Rio de Janeiro, Brazil, to a 

 bay on the coast of Portugal a few months later. 

 The Direct United States Cable Company 

 was formed, and laid a line from Ballenskill- 

 ings Bay, Ireland, to Rye, N. H., via Nova 

 Scotia, in 1874. The same year a sixth line 

 across the Atlantic was laid from Ireland to 

 Newfoundland, and in 1880 another French 

 line was laid from Brest to St. Pierre, an is- 

 land in the Gulf of St. Lawrence. In 1884- 

 '85, the companies owning all these lines hav- 

 ing previously formed a combination to keep 

 up rates, a competing company was formed by 

 James Gordon Bennett and Mr. Mackay, who 

 laid two lines from Ireland to Nova Scotia, 

 and also a connecting line from Ireland to 

 France. The difficulty with these submarine 

 cables at first was to send through them a cur- 

 rent of sufficient power to record the message. 

 The method adopted is as follows : Two keys, 

 which when dep'ressed transmit respectively 

 positive and negative currents, are employed 

 at the sending station, in connection with the 

 battery. The current of the battery does not 

 pass directly into the cable, but into a con- 

 denser, which passes it into the submarine 

 line. This greatly increases the force of the 

 current used, and serves to cut off interfering 

 earth-currents. The receiving-instrument first 

 employed was a reflecting galvanometer. 

 Upon the magnet of this instrument is carried 

 a small curved mirror. About two feet in 

 front of it is placed a lamp behind a fra.me in 



which is a vertical slit, while above it is a 

 screen. The light from this lamp, passing 

 through the slit, falls on the surface of the 

 mirror, which throws it back upon the screen. 

 The flash of light, moving from right to left 

 with the motion of the needle, indicates the 

 message sent. This method, however, has 

 been of late years almost entirely superseded 

 by an invention called the syphon galvanome- 

 ter. In this the movements of the needle are 

 recorded by means of ink spurted from a fine 

 glass syphon-tube. This tube is attached to a 

 coil suspended between two fixed magnets, 

 which swing to right or left as the pulsations 

 of the needle pass through it. The possibility 

 of laying an electric cable in the Atlantic from 

 Europe was suggested by Professor Morse as 

 far back as 1843, but it was not until 1854 that 

 Mr. Cyrus W. Field discussed the means of 

 practically realizing the idea, and it is to his 

 energy that the successful completion of this 

 great work is due. 



Aurora Borealis. Since the discovery 

 of electricity, and especially electro-magnetism, 

 all speculation on the nature of the aurora has 

 taken in that force as a principal element, and 

 modern experiments have been especially 

 turned to securing proof of the electric nature 

 of the auroral display. The theory advanced 

 by M. De La Rive, a Genoese scientist, and 

 which is generally accepted, is, that the aurora 

 is caused by the recomposition of the positive 

 and negative electricity, always to be found in 

 the upper and lower strata of air respectively. 

 Miniature auroras have been produced by 

 electricity by M. De La Rive, and also by a M. 

 Lenstrom. In M. Lenstrom's experiments, 

 which were made in Finland in 1882, the peak 

 of a mountain was surrounded with a coil of 

 copper wire, pointed at intervals with tin nibs. 

 This wire was charged with electricity, and a 

 yellow light was produced on the tin points, in 

 which the spectroscope analysis revealed the 

 greenish yellow ray that characterizes the au- 

 rora borealis. The aurora was supposed to be 

 of supernatural origin by the ancients. 



Armor. The warlike Europeans at first 

 despised any other defense than the shield. 

 Skins and padded hides were first used ; and 

 brass and iron armor, in plates or scales, fol- 

 lowed. The first body armor of the Britons 

 were skins of wild beasts, exchanged, after the 

 Roman conquest, for the well tanned leathern 

 cuirass. This latter continued until the Anglo- 

 Saxon era. Hengist is said to have had scale 

 armor, A. D. 449. The heavy cavalry were 

 covered with a coat of mail, 1216. Armor be- 

 came exceedingly splendid about 1350. The 

 armor of plate commenced, 1407. The armor 

 of Heary VIJ. consisted, of a cuirass of steel, 



