314 Intelligence and Miscellaneous Articles, 



The apparatus, which is called the " electrical valve/' and which is 

 analogous in construction to the apparatus known as the " electrical 

 egg," consists of a small hollow glass cylinder of ahout the size of 

 an ordinary drinking-glass, and closed below by a metal cap by which 

 it can be screwed on the air-pump, while the top is closed by a 

 tightly-fitting glass plate. In this plate there is a platinum wire 

 which terminates flush with the lower surface of the plate, and 

 externally can be joined to any conduction arrangement. In the 

 inside of the cylinder there is a brass disc 25 millims. in diameter, 

 supported on a brass stem, parallel to the covering plate, and at a 

 distance of 2'3 millims. from it. When the valve, in which the 

 air is rarefied to 1 or 2 lines of mercury, is introduced into the 

 wire of the secondary current of the battery, the deflection of the 

 needle of a multiplier interposed in the conduction ensues, in the 

 one direction or the other, according to the position of the valve. 

 The needle is deflected in the direction of a current, which has the 

 same direction as the principal current when it proceeds from the 

 disc, and in the opposite direction when it first meets the point. 

 From this the following convenient rule is obtained : — By means of the 

 electrical valve, and in any 'position, the secondary current of the Ley den 

 jar deflects a magnetic needle in the direction of a current proceeding 

 from the disc to the point of the valve. 



First, a multiplier with double needle was used ; and as this was 

 unfit for comparative experiments, a galvanometer was substituted 

 in which a steel mirror suspended by a cocoon-thread was deflected 

 by an adjacent coil of wire. The deflection by a feeble secondary 

 current was four times as great as that produced by the principal 

 one, and was not changed by the use of two valves. Experiments 

 which the author had previously made on the simultaneous magnet- 

 ization of three needles were repeated by inserting the valve in the 

 lateral circuit. The magnetization produced by the secondary cur- 

 rent was in the direction denoted by the deflection of the needle ; 

 and the influence which the secondary exercises was perceptible when 

 it was used in conjunction with the primary current for magnetizing 

 a needle. The secondary current alone affords the easiest and most 

 powerful means of imparting magnetism to a needle by means of the 

 Leyden battery. 



In a battery-circuit which, either by its great length or a special 

 arrangement, affords no opportunity for developing a powerful 

 secondary current, the valve is without action upon the magnetic 

 deflection, but not so as regards the magnetization of the needle. 

 This is strongest w r hen the discharge proceeds from the disc to the 

 point of the valve, thus confirming earlier experiments on the heating 

 of the circuit. 



The currents of higher order, which were investigated as far as 

 the fifth order, deflected the magnetic needle by the same rule as 

 that for the secondary current. The experiment is easy and certain 

 in all currents ; for it was invariably successful, provided the pressure 

 in the valve was not less than 2 lines, and not more than 5 inches of 

 mercury. By an individual deflection experiment, a current of higher 



