THE HONGKONG GOVERNMENT GAZETTE, 15TH MAY, 1886.
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diameter into which a piston, attached to the lower end of the rack, carrying the time-ball, producing a current of compressed air, that arrests the final descent of the ball without shocks ussion. In addition to different circular openings on opposite sides of the pneumatic cylinder, nished with Varley's pressure relieving valve, which enables, by means of tightening a spring, unt of compression produced in the cylinder to be regulated and a greater distinctness to be in the signal. The spring at present is so adjusted as to cause the ball to rebound half a foot ost a foot, which is not noticed by an observer whose attention is riveted on the very beginning rop, which is best observed in a small binocular. Any one who looks at the drop with his naked ay see the final rebound, but this is rather an indication that the very beginning of the drop was curately observed by him-About half a pint of oil is kept in the pneumatic cylinder and the nt of the rebound partly depends on this oil, a greater quantity of oil or water causing a larger had. Any rainwater that has found its way into the cylinder is therefore allowed to run out h a tap in the bottom at a quarter to one o'clock.-The ground floor affords room for keeping the ological signals, when not in use.
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loch. The ball is hoisted by aid of toothed gearing, a lever throwing the pinion, that the forged iron rack in and out of gear as required. A girder passes across the centre ant stands when winding up the ball and ball and through the slot cut in the upper projecting portion of the mast, which portion is teel. This girder is attached inside the mast to the per end of the rack by which the ball While the ball &c. is resting on the pinion, it is of course not possible to throw it out of ou is hoisted above the bolt of the lock, which is previously set, and slowly lowered. When can be thrown out of gear, it shows that the piston with its superincumbent weight of nearly securely resting on the bolt of the lock.
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electric lock is enclosed in a wooden box, which covers and protects it. It has only one perture through which the bolt protrudes. One side is glazed and allows the interior to be It has also a small door through which the hammer is raised, which operation sets the lock the locking current.
mometer a series of levers inside the lock, the time occupied in discharging which does not exceed at of bolt on which the ball hange, is liberated by a blow from the very small brass hammer acting sensitiveness and rapidity of action is obtained by the greatest accuracy of ving and ent, so that the friction rollers attached to the levers in their discharge move over planes at an exactly 90 degrees. If the angle be greater, when the piston is lowered on to the bolt, the ll be to discharge the lock by the weight resting on the bolt, and therefore the apparatus lepressingesting, on the bolt and a much greater force than is available will be required to discharge it, pe set. Should the angle be less, then the apparatus will be firmly fixed by the weight of the correight would have to be lifted through a small space before the bolt could be discharged. ssing the
charging ature, which strongly attracts the poles of a soft iron magnet, wrapped with insulated wire and VARLEY constructs these electric locks on the polarized system. The trigger is a jointed soft e galva inductively magnetic by a powerful compound permanent magnet. A spiral spring attached ing each d to the armature and at the other to an adjusting screw is so adjusted as to nearly overcome electric Active force existing between the armature and the polarized electro-magnet. ball and arrives, polarizes the electro-magnet in the opposite direction to that induced by the permanent in thend the effect is to release the armature, which is at once pulled away by the tension of the › ball at ghich is however less than an ounce, and to discharge the lock with great rapidity.
The time current
ometer advantages claimed for the polarized system, apart from its rapidity of action and greater t some mess, is that by closing the circuit, as Mr. VARLEY does, in the first instance (when the piston quarter on the bolt of the electric lock previous to the arrival of the 1 o'clock current), with say a current, which increases the attraction between the armature and the soft iron magnet, and opping the clock at 1 p. reverse the direction to a positive current, that reverses the polarity of the coast, magnet, the trigger is electrically locked, up to the time of sending the discharge current, and public cking current is stronger than any current likely to be produced by accidental contact with three circuit, the greatest security is obtained, that the ball does not fall before the circuit is closed those clock in the observatory.
ewhat explained above, the electric lock is discharged at 12 h, 50 m. Os. by touching the left hand he relay in the observatory. This shows, that the line &c., is in proper order and gives correct ds in the assistant in the tower. hich 40s. he sets the lock, which is indicated in the observatory by deflection of the right hand galva- horr, the hand of which then indicates "locked."
At 12 h. 55 m. he begins to hoist the ball half mast. alf when the piston touches the bolt, this is indicated in the observatory by vibrations of the galvano- epahand, caused by the bolt alternately touching the side of the piston and falling into horizontal, At 12 h. 57 m. he begins to hoist the ball to the At 12 h. caped groves cut in its surface. When the piston ascends above the lock, the bolt falling into
gives an audible click after which the piston is lowered on to the bolt and the pinion thrown Igear. From this time till one o'clock the ball rests on the bolt of the lock. This is indicated 66ncrease in the deflection on the galvanometer in the observatory and also on a galvanometer in inover situated on top of the lock, which increase is caused by extra earth-connection being yed through the mast &c., of the apparatus. The galvanometers are read off in both places and edications entered in the "time-ball journal."
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