268 Correspondence of J. Nickles. 



Effects with Ruhmkorjf } s Apparatus of Induction. — M. Leon Foucauli 

 has been engaged for some time in studying the effects of the apparatus 

 of Ruhmkorff. In place of using only a single apparatus, he operates 

 with four, which are united so as to work together by means of a peculiar 

 interrupter, — a mercury interrupter. In the open air, four machines of 

 ordinary dimensions, under the action of ten couples of a Bunsen's large 

 battery, give a spark at a distance of seven centimeters (nearly three 

 inches). 



The addition of a condenser in which the armature acts on a surface of 

 30 to 50 centimeters, renders the spark very bright, and reduces the ex- 

 plosive distance to 18 millimeters. The series of discharges, which fol- 

 low one another with rapidity, give to the point where the operation is 

 going on, a light like that of an ordinary lamp. Although the bright- 

 ness from such a source does not appear excessive, it acts on the organs 

 of sight, when observed directly, like, the light from the carbon of the 

 galvanic circuit, producing a painful sensation which may continue for 

 hours afterward. The interposition of glass of uranium prevents or di- 

 minishes very much this effect, which appears to show that it is due to 

 the very refrangible and in part invisible rays which constitute in large 

 proportion the electric light. 



The discharge of the four instruments traverses easily a tube exhausted 

 by an air pump two metres long; a column of light is developed from 

 one end to the other and presents throughout its extent a kind of stratifi- 

 cation, such as has been noticed in the interior of the electric egg. 



Electric Chronometers. — The ingenious artist, M. Breguet, son of the 

 skillful mechanician who invented the Breguet Thermometer, etc., has de- 

 voted himself to the construction of chronometers in connection with the 

 Electric Telegraph. During his recent stay at Paris, he has placed a 

 chronometer of great simplicity in a gas lamp. It consists of a dial armed 

 with two needles moved by electricity, which mark the hours and minutes. 

 The whole mechanism consists of three wheels, a pinion, an escapement, 

 and a double rachet, with a means of reversing the current : two wires 

 pass from the lamp to a regulating clock situated in the apartment of M. 

 Breguet. This inventor proposes to divide Paris into 12 electric districts, 

 and place in each mayoralty a regulator which shall distribute time 

 throughout the district both to the public lamps and private houses. 



Gas and Steam Manometer Alarm. — The same artist has made another 

 application of electricity. He has constructed an apparatus for informing 

 the engineer either of gas or steam apparatus, by the stroke of a bell, 

 that the pressure is above or below what is required. It is accomplished 

 in a very simple manner. At the extremities of the arc which the nee- 

 dle of the manometer passes over, there are put two metallic points which 

 limit its movement in either direction ; the contact of the needle with 

 these metallic points is made to close a circuit proceeding from a small 

 battery, and this puts the bell in play. 



On a Cause of Atmospheric Electrieity. — There exists between the liv- 

 ing plant and the soil supporting it an electric current, which always 

 moves in the same direction, that is, the soil is constantly positive, the 

 plant continually negative. This fact, was first observed by M. Becquerel, 

 Sr., and for several years it has been pointed out by him as one of the 



