160 ANNUAL OF SCIENTIFIC DISCOVEllY. 



of large quantity is required. Experimenting with it lateh^ I be- 

 came satislied of the cause of this defect. Akhough there may 

 be a large reservoir of liquid, only the stratum between the plates 

 is active, and, as no gas is being given off, there is no circulation ; 

 this soon becomes exiiausted, and as it is renewed merely by dif- 

 fusion, can only maintain a current equivalent to the fresh supply 

 of liquid thus obtained. I therefore used a thin beaker as the 

 containing vessel, and placed it over aBunsen's burner capable of 

 maintaining a moderate circulation of the liquid, and as 1 expect- 

 ed, the battery now gave its fnllest force with absolute constancy, 

 until the complete exhaustion of the exciting fluid. Mechanical 

 stirring of the liquid or motion of the plates will produce a similar 

 result; and thus by any of the various modes which may be em- 

 ployed, this battery can be made to yield a current more powerful 

 than any other known form, without giving oif any noxious gases, 

 and as absolutely constant as can be desired. — John T. Spkague, 

 in Chem. News. 



ELECTRIC CLOCKS. 



A new form of electric clock, invented by M. L. De Combettes, 

 consists of a long pendulum, on the lower portion of which is fixed 

 the clock-face. The weight is a sort of box containing an electro- 

 magnet and armature, which, on being attracted, disturbs the 

 equilibrium of the pendulum, and consequently gives it motion. 

 The movement of the armature transmits motion to the hands of 

 the clock in a manner somewhat similar to the mechanism of the 

 alphabet-dial telegraph instrument. In order to make and break 

 the electric circuit, the movement of the pendulum is made use of, 

 one pole of the battery being connected permanently, through the 

 axis of suspension, to one end of the electro-magnet, whilst the 

 other pole is connected to a metal plate, against which a point of 

 the pendulum, in connection with the electro-magnet, makes con- 

 tact at every beat, thus completing the circuit and causing the 

 electro-magnet to attract the armature. It is stated that only a 

 weak battery is required, and that two DanielPs cells will keep it 

 working for several months. 



An electrical clock in the rotunda of the Philadelphia Merchants' 

 Exchange has a running gear consisting simply of two cog-wheels 

 and a ratchet-wheel. The driving power is supplied by a weak 

 galvanic battery, the currents from which, transmitted through two 

 galvanometer coils, placed one on each side of the clock-case, act 

 upon steel bar magnets set within the ijendulum ball. The latter 

 swings between the two coils, so that when one is positively 

 charged the ball is attracted until, by contact, it becomes similarly 

 electritied, and consequently repelled; then, swinging over to the 

 negative coil, it becomes negatively charged, and again repelled ; 

 and thus the vibrations are kept up indefiniteh', or as long as tlie 

 •battery continues working. The alternate positive and negative 

 charges are made and broken by a simple slide-bar moved by a 

 wire pin on the pendulum-rod. — Mechanics' Magazine. 



