EXHIBITION OF ELECTKICITY AT PAKIS. 



tinctly in the telephone. It was by placing 

 microphones on the stages of Paris theatres, 

 connected with telephonic receivers in the Ex- 

 position building, that every sound of an opera 

 could be heard 1>\ visitors at the International 

 Exhibition of Electricity, as distinctly as in any 

 part of the Opera-llouse. 



The " pantelephone " of Ldchet Labye, a 

 Belgian inventor, is not only one of the sim- 

 plest microphones yet made, but is one of the 

 most sensitive transmitting ordinary speech, 

 uttered at distances of thirty or forty yards, 

 and the lowest whispers spoken several feet 

 away. It consists of a plate of cork, six inches 

 by four, hung at one side on two pieces of thin 

 watch-spring, one of which is connected by a 

 wire with a button of hard carbon imbedded 

 in the cork, which is pressed upon by a brass 

 hook working on a hinge. The transmitter is 

 connected in the usual way with a battery and 

 induction-coil. 



Professor Dolbear has invented a speaking- 

 telephone in which no magnet is used in the 

 receiver. The transmitter is a form of the mi- 

 crophone. The receiver is formed by two met- 

 al plates or diaphragms, electrically insulated 

 from each other, and held parallel in a wooden 

 frame. One of the plates is connected to the 

 telephone-current, and the other to the earth. 

 Being oppositely charged, the vibration pro- 

 duced in one of them by the current sets up 

 audible vibrations in the other. 



Dr. Cornelius Ilerz has advanced a step in 

 the construction of telephones by discarding 

 the magnetic receiver, and disregarding the 

 principle of magnetism. With his instrument 

 he succeeded in conveying audible speech along 

 a wire 800 miles in length. The only battery 

 used was a single Lechanche element. 



The electric arc, placed in a vacuum, as was 

 observed by Davy, the discoverer of the arc, 

 becomes elongated, and the carbons are no 

 longer consumed. The experiment has been 

 repeated by Jamin, with results which promise 

 to give a new form to arc-lamps in the future. 

 Gases which have no action upon the carbons 

 as nitrogen, acetylene, carbonic oxide, and 

 marsh-gas answer the purpose as well as a 

 vacuum. If the carbons are inclosed in a 

 sealed vessel containing ordinary air, the oxy- 

 gen is taken up by the carbon, leaving only 

 nitrogen and carbonic oxide in the vessel. The 

 light in the closed vessel is absolutely even and 

 steady. Its spectrum is like that of carbu- 

 retted gas traversed by the spark of a Ruhm- 

 korff coil, or like that of the comet of 1881, as 

 observed by Thollon and others, being the elec- 

 tric spectrum of incandescent carbon-vapor. 

 Whether the carbon is of good or of very poor 

 quality, the flickering, which is never entirely 

 absent in open-air lamps, is avoided altogether. 

 The arc gives a full, distinct, and perfectly 

 changeless light, of a greenish-blue tinge. The 

 red and wavering light of open-air arc-lamps 

 is due to the combustion of the carbons and 

 their inequalities. A single Jamin candle in 



the ordinary apparatus lasts two hours, but in 

 the atmosphere of inactive gases, in a hermet- 

 ically sealed globe, each candle burns 160 hours, 

 and the lamp with five candles burns 800 hours 

 without change or attention. 



The mechanical arrangements for feeding the 

 carbons in the arc-lamps are exceedingly va- 

 rious, and are being constantly improved upon. 

 Siemens and Brush have an arrangement by 

 which a pair of carbons that are burned out 

 are automatically replaced by a fivsh pair. 

 The Belgian lamp invented by Jaspar is regu- 

 lated by a magnet within a solenoid which sup- 

 ports the upper carbon, and is raised and low- 

 ered by the varying power of the current. 

 The English light of Andrews contains electro- 

 magnets which act upon a clutch holding the 

 carbon. In the latest form of the Gramme 

 lamp there is an arrangement of electro-mag- 

 nets and clock-workmachinery which allows the 

 upper carbon to fall at the rate of only a tenth 

 of a millimetre at each step : one magnet ad- 

 justs the carbons at a proper distance apart, as 

 soon as the current begins to pass; and when 

 the main current becomes weaker, that in the 

 second magnet is strengthened and causes the 

 clock-work to move. 



Recent improvements in lamps of the semi- 

 incandescent type, exemplified by the candle of 

 Jablochkoff, have been made by Jamin, Debrun, 

 and others. Rods of plain carbon are used in- 

 stead of kaolin or other substance whose in- 

 candescence gave a colored light. Jamin sur- 

 rounds the rods with coils of wire, with a space 

 between the coil and the candle. The inductive 

 action of the current in the coils drives the light 

 a distance beyond the ends of the candles. De- 

 brun's similar light has an arrangement for in- 

 stantaneously relighting a lamp which has gone 

 out, by means of a commutator, which causes 

 a piece of carbon to join the two candles estab- 

 lishing the current, which then repels the cross- 

 piece and re-illumes the arc. The lampe-aoleil 

 is a steady light in which a block of marble is 

 rendered incandescent by the current between 

 the carbons. 



The Brussels meteorograph is an instrument 

 which records and automatically telegraphs 

 to a distance, where they are reproduced on a 

 revolving drum, the readings of the wet and 

 dry bulb thermometer, the barometer, the ane- 

 mometer, and the rain-fall. The drum contains 

 the curves giving the readings of the various 

 instruments every ten minutes, for a period of 

 five days. A Swedish form of the meteoro- 

 graph records observations at intervals of fif- 

 teen minutes, and requires no attention for 

 months at a time. 



Four forms of incandescent filament-lamps 

 were exhibited at the Paris Electrical Exposi- 

 tion. The Swan lamp is little more than a 

 repetition of Edison's. The carbon filament is 

 a piece of cotton thread, treated with acid and 

 carbonized by baking in an intensely high tem- 

 perature. It is burned in a vacuum globe, be- 

 ing attached at its two ends to platinum con- 



