MECHANICS AND USEFUL ARTS. 89 



of Xcw York City. Its chief peculiarity consists in its motive power. Upon 

 the circular metallic plate which forms the base of the clock is firmly fixed 

 an upright steel screw, standing from ten to fifteen inches in height. A 

 metallic ball of about two pounds weight is penetrated through its centre by 

 this screw, and when at the upper end tends to run down the spiral inclined 

 plane by revolving around it. By an ingenious arrangement, it is made to 

 roll upon a little wheel attached to the top of the weight, without itself 

 touching the screw; the friction is thus reduced to the least possible amount; 

 and as by raising the weight this little wheel starts back and again catches 

 in the thread of the screw at whatever point the weight is lifted, the only 

 winding up required is simply to raise the weight, and for this a rod is pro- 

 vided, the upper end of which terminates in a ring or knob outside the clock, 

 and the lower end in a circle, which 'takes the base of the weight as the rod 

 is lifted. The revolution of the ball is communicated to the main wheel, 

 which lies horizontally upon the bottom of the plate, by means of two rods 

 that pass through the bull and are fixed to this wheel. A horizontal bar 

 connects their upper ends, and the middle point of this bar is supported and 

 turns upon the top of the screw. On this centre is the wheel, attached to 

 the upper surface of the cross-bar, which regulates the movement of tho 

 hands upon the dial. The main wheel at the base is connected immediately 

 with the escapement and balance-wheel, by which its motion is checked, and 

 let out tick by tick with each swing of the balance. In these clocks the 

 balance is on the compensation principle. The regulation is like that of a 

 watch, and is reached by a wire introduced, when required, through a little 

 hole made in the glass for this purpose. From the perfection of the works, 

 and the holes beijig jeweled, the clock runs at regular rates, and as a time- 

 keeper is probably not surpassed by any other of the same cost. The works 

 arc perfectly protected from dust, and the hands are covered by a glass like 

 that of a watch, or, when inclosed, as in some of the clocks, under the glass 

 cylinder, they may be reached through a hole made opposite to them in the 

 glass, by a long key constructed for this purpose. 



The important points in this clock are: first, the uniform manner of action 

 of the motive power; second, its direct action upon the main wheel without 

 the intervention of toothed wheels, which in other clocks introduce addi- 

 tional friction and causes of irregularity. The motive power required is thus 

 lessened, and the wear proportionably reduced. It is variously constructed 

 with one to three dials, and to run thirty-six hours, fifty hours, or eight days- 

 For family use, no inconvenience is experienced in the use of those which 

 run only thirty-six hours, as the position of the weight is at all times seen, 

 and whenever at a low point is readily lifted by any member of the family. 

 N. Y. Tribune. 



RECOVERY OF SILVER FROil SILVER-PLATED UTENSILS. 



An important problem was that of readily obtaining pure silver from old, 

 wora-out plated utensils of copper, etc. A recent number of the Munitcnr 

 Scientifique publishes valuable information on the subject, by M. Soelzel. 

 The best method consists of treating the plated work by sulphuric acid, in 

 which from five to ten per cent of nitrate of soda has been dissolved. The 

 silver disappears, as if by magic, in this solution, before any of the copper is 

 at all acted upon. 



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