76 Chronicles of Science. [Jan., 



of Pulkowa. On the frame of the clock, one on each side of an ima- 

 ginary plane, which would cut the centre of the crutch, are fixed two 

 ivory cylinders, each of which having cemented in it a capillary tube 

 of glass ; these two capillary tubes are open and point to one another, 

 and are connected with two reservoirs of mercury, so that a stream of 

 that metal issues from each capillary tube, and these two streams 

 uniting, form, as it were, a wire of mercury connecting the two reser- 

 voirs ; and these reservoirs being connected with the respective poles 

 of a battery the circuit is completed, and the current continually 

 transmitted so long as the mercury-wire remains unbroken. The 

 breaking of the circuit at the desired intervals is thus effected. To a 

 prolongation of the ordinary crutch is attached a thin blade of mica, 

 capable of adjustment as to position ; and this blade of mica as the 

 pendulum and crutch oscillate, cuts through the mercury-wire, thus 

 breaking the circuit and causing the signal to be transmitted. The 

 position of the mercury-wire and that of the mica-blade being 

 capable of adjustment with reference to each other, break of contact 

 can be made to coincide absolutely with the beat of the clock, and the 

 duration of the break can be regulated by varying the width of the 

 blade of mica. 



With further reference to the subject of the transmission of correct 

 time, Mr. De la Rue states that the Liverpool Observatory is about to 

 be removed to the Birkenhead, or opposite side of the Mersey, so as to 

 make room for dock improvement ; but, in order that its great utility 

 to the mercantile navy may not be interfered with, it is intended to 

 place a chronometer room in a position easly accessible to mariners, 

 and to transmit time signals to and control the clock of that establish- 

 ment by means of electric communication with the normal clock of 

 the observatory. Jones's system of controlling clocks has been for 

 some time past successfully practised in Liverpool, where the value 

 of accurate time is fully appreciated ; and we all know that in 

 Scotland the transmitting of time signals, either by gun-firing or by 

 controlled clocks, has created a great sensation. London, however, 

 is still deficient in this respect ; and notwithstanding the admitted 

 truth of the adage, " Time is money," and the proximity of Greenwich, 

 accurate time is not obtainable at any public establishment, whereas 

 one would imagine that in the City, at least, controlled clocks would 

 be placed in the various centres of commercial activity. Mr. De la 

 Rue relates that he can speak from his own personal experience as to 

 the practicability of transmitting time signals, and controlling clocks by 

 electric agency, for in his own works, Mr. Walker, in conjunction 

 with Mr, Jones, lias, by the kind permission of the Astronomer- 

 Royal, placed a clock so perfectly under the control of the Greenwich 

 clock, that unless there is some derangement of the wires, it beats for 

 months consecutively, second for second, with the clock at Greenwich ; 

 and in case of an occasional variation, a signal comes four seconds 

 after every hour, and furnishes a means of correction. 



With a view to the determination of the parallax of the fixed stars, 

 Dr. Winnecke, the vice-director of the Pulkowa Observatory, is having 

 erected in a small observatory at a little distance from the main building, 



