252 



ELECTRICITY. 



ENGINEERING. 



rent. In the third method a differential ther- 

 mometer was used, consisting of two hollow 

 iron cores, communicating by a capillary tube 

 in which was a liquid index : every heat-action 

 in the one core was followed by an expansion 

 of the contained air, and displacement of the 

 index. 



In order to determine the cause of the de- 

 velopment of heat, M. Cazin proceeded as fol- 

 lows: 



Kound the iron core in the petroleum thermometer 

 two coils of 480 turns were passed, one of them being 

 in the interrupted magnetizing circuit, while the 

 other formed a special circuit, which at each turn 

 of the interrupting apparatus was closed. The first 

 coil could now induce a current in the second, if 

 the closures of the two circuits took place at the 

 proper times, as might be arranged at will. These 

 experiments gave the greatest development of heat 

 when the circuit of the second spiral remained con- 

 tinually open. The heat was not altered when the 

 circuit was closed at closing of the magnetizing cur- 

 rent. There is thus no thermal action during the 

 variable period of closure. Lastly, the heat was 

 smaller when the circuit of the second spiral, dur- 

 ing the opening of the inducing circuit, was closed: 

 it went down as much as the half. " It thus proved 

 that the production of the magnetic heat takes place 

 during the opening of the voltaic circuit; conse- 

 quently, that it accompanies the disappearance of 

 magnetism in the core." 



The decrease of heat in this last case is ex- 

 plained on the principle of thermo-dynamics. 

 The disappearance of the magnetism is the 

 cause of the appearance of a certain quantity 

 of heat. When no circuit is near, in which an 

 induced current can arise, then the whole of 

 this heat appears in the core ; but, when induc- 

 tion occurs, a part of the heat appears in the 

 induced circuit, and the rest remains in the 

 core. The cessation of the magnetization is 

 an operation in which the magnetic energy de- 

 creases and is transformed into heat-energy, 

 either in the core or in the neighboring masses 

 which are in a position to be the seat of in- 

 duction phenomena. 



Improved Electric Railway -Signal. A sim- 

 ple and effective application of electricity to 

 railroad signaling is in use on the Boston, 

 Lowell & Nashua Railroad. The apparatus is 

 described and illustrated with a woodcut in the 

 Scientific American. Its principle will be 

 readily understood from what follows : A sin- 

 gle-cell Callaud battery is connected to the two 

 rails at one end of a given section of the line 

 (say two miles in length), each section being 

 insulated from adjoining sections. At the other 

 end of the section the signal has an electro- 

 magnet similarly connected to the two rails. 

 AVhen the circuit is closed, as is normally the 

 case, the magnet is excited and the signal 

 controlled thereby, so as to show that the 

 line is clear. But when a train enters on the 

 section, then a shorter circuit is made by the 

 wheels and axles, and the current returns to 

 the battery by this course instead of passing 

 through the signals. The magnet ceases now 

 to attract, and the signal, by mechanical means, 

 is at once turned to indicate danger. It is ob- 



vious that this must occur as long as a single 

 car remains on the track, or when the circuit 

 is broken by a displaced or broken rail, or any 

 other cause. Hence the device may be applied 

 over an entire line, and will indicate the condi- 

 tion of every section to a train about to enter 

 on the same. It is not affected by changes of 

 weather. 



ELIO, JOAQUIN, a Spanish general, died in 

 January, 1876, very much advanced in years. 

 He was educated for service in the royalist 

 army in Spain, in which he obtained his first 

 commission. During the progress of a stormy 

 public career, he served under many govern- 

 ments. In 1860 he commanded a part of the 

 Carlist insurgents, and during the last Carlist 

 War he also acted with Don Carlos, by whom 

 he had been threatened with the loss of his 

 command, and with court-martial, on several 

 occasions. In 1860 he was captured by Queen 

 Isabella's forces, and was only saved from 

 death by the clemency of the Queen. On that 

 occasion, he wrote a letter to the Queen, iu 

 which he promised never again to take part in 

 any movements against her ; but, nevertheless, 

 he fought in the Carlist War against her son, 

 Don Alfonso. Don Carlos appointed him in 

 1873 captain-general of the Carlist forces, and 

 Minister of War. He conducted the operations 

 of the Carlist forces against Bilbao, and the 

 defense of the line of Sommorastra. in 1874, 

 and, when the Carlists were repulsed there, 

 he resigned his position, but remained with the 

 army. 



ENGINEERING. The art of engineering 

 has made great strides in late times, and, with 

 the growth of commerce, has been put more 

 and more into requisition to devise and con- 

 struct shorter and easier avenues of communi- 

 cation. In all progressive countries gigantic 

 works are constantly in progress, requiring 

 millions of outlay and years of labor, while 

 still greater undertakings are being seriously 

 proposed, such as would formerly have been 

 considered fond and idle dreams. Among 

 them may be mentioned the connection of the 

 Black Sea with the Caspian by a ship-canal; 

 the construction of an artificial channel be- 

 tween the great rivers of Central Africa, so 

 as to make a navigable water-way across the 

 continent; the cutting of a passage between 

 the sea and the low bed of the -great African 

 Desert, by which a great portion of the sandy 

 waste would be submerged, and wide districts 

 rendered fertile; the building of a great ship- 

 canal through Southern France from the bay 

 of Biscay to the Mediterranean ; the widening 

 and deepening of the Seine, eo as to make 

 Paris a seaport. 



It is worthy of note that the chief engineer- 

 ing projects of the most recent times look 

 toward the extension and improvement of 

 water -communication. The construction of a 

 ship-canal through the American Isthmus, 

 which has long been a cherished project of the 

 American people, may be said to be on the 



