348 History of' Mechanical Inventions and 



ing the plate, and rubbing sheep's suet (from the animal) over it, and 

 keeping it near a fire, or in a dry room. The best steel plates are those 

 manufactured by Mr Rhodes and Mr Hoole of Sheffield. See the Trans- 

 actions of the Society of Arts, 182*, vol. xlii. p. 50. 



9. Description of' Lenormand's New Chronometer. 



This very singular piece of mechanism, which excited much interest at 

 the expositions of French industry in 1819 and 1823, is represented in 

 Plate VI. Figs. 5, 6, 7. The principle of this chronometer consists in 

 the continual displacement of the centre of gravity of the arm of a lever. 

 This lever has the form of an arrow AB, Fig. 5. which is capable of 

 moving round a horizontal axis O, fixed in the middle of a dial-plate di- 

 vided into twelve hours. The two arms AO, BO are unequal, and at the 

 end B is fixed a round box. If we place in the box a small weight, 

 which has the power of moving round the interior circumference of the 

 box, and if it is placed as at B, the arrow will remain in the position AB, 

 and point to IX k . If the small weight is placed as at D, so as to be at the 

 greatest possible distance from the centre O, the arrow will point to XII h , 

 and so on at the other quarters, as at £ and F in Fig. 6. In like manner, 

 intermediate positions of the little weight will cause the arrow to point to 

 intermediate hours. If we now could fix in the box a piece of wheel- 

 work to displace this weight in a regular manner, so as to describe the 

 circumference of the box in twelve hours, the arrow AB would revolve in 

 twelve hours, and would point them out on the dial-plate like the hand of 

 a clock. If the wheel- work should carry the weight round the box in 'an 

 hour, the arrow would mark minutes on the dial. The additional weight 

 which we have used for the purpose of explaining the principle of the 

 machine, is not actually used. It exists naturally in every watch, as the 

 centre of gravity of every watch is at a distance from its centre of form, 

 on account of the weight of the main-spring box and fusee. We require, 

 therefore, only to place a watch in the box B, Fig. 5, in such a manner, 

 that it cannot go without communicating its motion to the arrow AB. 

 This may be done in two ways, 1, The axle of the central wheel, at the 

 place where it comes out of the plate in which it moves, carries a square 

 which is laid hold of by one of the two cross pieces between which the 

 watch is carried, which cross pieces are fixed to the box. The other end 

 of the axle, which is round, moves in a hole perforated in the opposite 

 cross piece. This method, though the most simple, is not always so con- 

 venient as the following : 2, On one of the cross pieces above mentioned 

 is fixed a wheel 0, Fig. 7. which cannot turn round. Above the plate of 

 the watch passes the axle of a wheel, on which is fixed a pinion R, which 

 works in the wheel O. The wheel-work actuated by the spring not 

 being able to turn the wheel O, turns quite round it, and, consequently, 

 carries the centre of gravity of the watch quite round the interior circum- 

 ference of the box B, Fig. 5, and this changes at every instant, and in 

 a regular manner, the centre of gravity of the arrow. If the axle of the 

 wheel, which carries the pinion R, turns round in one hour, and if we 



