NATURAL PHILOSOPHY. 125 



MEANS OF CAUSING AN ELECTRICAL MACHINE TO WORK IN ALL 



WEATHERS. 



M. MUNCH states in the Comptes Ren Jus that he has discovered a 

 means of causing an electrical machine to work in all weathers. This 

 means consists in tracing a slight line of tallow on each side of the 

 plate from the centre to the circumference. If this be done in weather 

 when scarcely any thing can be got from the machine, it will be seen, 

 from the first turn of the plate, that every thing is changed, and that 

 it will perform perfectly. If the glass pillars which support the con- 

 ductor are not covered with a coating of gum-lac, tallow should also 

 be applied lightly to them, and then rubbed off with a dry cloth. It 

 is evident that in these operations the object is to interpose an imper- 

 ceptible coating of fatty matter between the surface of the glass and 

 the ambient air charged with aqueous vapor. 



ELECTRO-DYNAMOMETER. 



WEBER has invented a new and very ingenious instrument, which 

 he calls an electro-dynamometer. It consists of two coils of fine wire, 

 the smaller of which is suspended within the other by a bifilar suspen- 

 sion, so that their centres coincide and their axes are at right angles. 

 He calls the latter " the multiplier," the other " the bifilar (or rather 

 suspended) coil." They are so connected that the current to be ex- 

 amined, traversing the multiplier, passes by suspending wires through 

 the suspended coil, which turns by their mutual action through an 

 angle, whose tangent measures the intensity of their action. The 

 angle is measured, as in the German magnetometers, by observing 

 with a telescope the reflection of a scale placed at a considerable dis- 

 tance in the mirror, carried by the bifilar coil. The action between 

 the coils is as the square of the intensity of the current, while that 

 exerted on the needle of a rheometer is simply as the intensity. Lord 

 Rossc's Address before the Royal Society. 



LAMP-LIGHTING BY ELECTRICITY. 



THE Paris correspondent of the London Times writes as follows : 

 " A rapid and scientific mode of lighting and extinguishing public 

 gas-burners has been invented by a person named Villatte. The open- 

 ing of the burner of each lamp is covered with a piece of soft iron, 

 mounted upon a hinge. In connection with this is a wire, extending 

 from a galvanic battery the entire length of the service of the gas- 

 lamps, and close to the orifice of each burner is a small slip of plati- 

 num. The soft iron, becoming a magnet when acted upon by the 

 electric fluid, opens or closes the orifice, according to the motion im- 

 parted to it ; the platinum ignites when it is necessary to light the 

 lamps ; and thus every lamp in a large town may be lighted or ex- 

 tinguished simultaneously, by a different action on the magnetized 



iron. ' 



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