752 



SCIENTIFIC RECREATIONS. 



MYSTERIOUS CLOCKS. 



The clocks represented in the two following illustrations (figs. 878 and 

 879), are well worthy of being placed in the house of any amateur of science. 

 They are made of transparent crystal, and though all mechanism is cleverly 

 concealed they keep capital time. The former clock (fig. 878) is the inven- 

 tion of Robert Houdin, and consists of two crystal discs superposed and 

 enclosed in the same frame. One carries the usual numerals, the other 



moves upon its centre with the minute 

 hand attached, and its rotation induces 

 by the ordinary method the move- 

 ment of the hour hand. The requisite 

 motion is transmitted to the dial by 

 gear disposed along the circumference 

 and hidden within the metallic frame, 

 and is itself put in motion by clock- 

 work, enclosed in the pedestal of the 

 timepiece. 



M. Cadot, in his clock (fig. 879), 

 retains the plates, but adopts the 

 rectangular form, so as to preclude all 

 idea of rotation, and to puzzle those 

 who are acquainted with the working 

 of Houdin's clock. The minute hand 

 cannot, in this instance, be fixed to 

 the second glass plate, it preserves its 

 independence. This movable plate 

 has only a very slight angular move- 

 ment around its centre, which oscilla- 

 tion or " play " is permitted in the 

 interior of the rectangular dial. A 

 little spring movement, hidden in the 

 central nut of the " hand," provides in 

 progressive rotation the oscillation of 

 the transparent plate, which cannot be perceived to move. 



To produce this " balance " motion the plate is supported upon a bar 

 in the lower part of the metal frame. After the direct oscillation of which 

 we have spoken, a little spring puts the machinery back. The direct dis- 

 placement is produced by a vertical piston which raises the end of the bar. 

 This piston rests upon a bent lever communicating with a wheel with thirty 

 triangular teeth. Finally this wheel turns upon its axis once in an hour by 

 a clockwork arrangement in the pedestal of the clock. Each tooth takes 

 two minutes to pass, and the movement is communicated to the minute 

 hand, which thus goes round the dial in the hour. The hour hand is con- 



Fig. 878. Houdin's clock. 



