XI. TIME. 93 



the school for middle-class education at Assen. Price about 41. The escape- 

 ment may be pulled forward so as to allow the wheel to turn freely. In this 

 manner it may be demonstrated, that clockwork without a pendulum will 

 acquire an accelerated motion. 



The escapement must be kept in a forward position, until the weight has 

 reached the ground. 



The apparatus, as it audibly indicates the minutes, may also be used for 

 experiments to demonstrate the laws of the pendulum, the laws of hydro- 

 dynamics, &c. 



461. Hew System of Electric Clocks. 



Prof. F. Osnaghi, Vienna. 



In these electric clocks the uncertainty of the action of the greater number 

 of electric pointers has been avoided by causing the electric stream to flow 

 with almost unabated force, as if there were no other clocks present. This 

 is attained by giving the electro-magnets double coils of very unequal 

 resistance. The spirals Avith great resistance serve for the attraction of the 

 needle from a distance ; the spirals with little resistance for retaining the 

 already attracted needle. With every clock there is also a wire coil for the 

 general return current, through which the electric stream can circulate until 

 the attraction of the needle is complete, "when its course is diverted by certain 

 mechanism, and is forced to pass over to the next clock. 



462. Model of a Clock with four Faces, to be worked 

 by water. Major M. L. Taylor, R.A. 



463. Sir W. Congreve's Clock, in which the action of 

 the pendulum is replaced by the motion of a small steel ball on an 

 inclined plane, which it descends in 30 seconds. 



Major M. L. Taylor, R.A. 



464. Model of a Frotomotive Clock. 



The Committee, Royal Museum, Peel Park, Salford. 



An apparatus consisting of a dial with hour and minute hands, and a gutta- 

 percha tube 100 feet in length, the object of which apparatus is to demonstrate 

 how a number of such dials in distinct situations may be made, by means of a 

 column of air at natural pressure, to indicate the same time as the clock with 

 which they are connected. Invented and made by the late Eichard Roberts, 

 C.E., Manchester, about the year 1848. 



465. Ley's Compensating Pendulum. Henry W. Ley. 



An inexpensive pendulum compensation is to be obtained by the employ- 

 ment of zinc and flint glass. 



466. Ley's Entirely Detached Gravity Escapement. 



Henry W. Ley. 



The object of this escapement is to cut off absolutely from the pendulum 

 the clock train with its variations, and thus to make the work of the pendulum 

 constant. The arrangement of the escapement shown in the Figs, permits 

 the motions of the various parts to be clearly followed. The scape wheel 

 has six long teeth A, Figs. 1, 2, 3, and 4, by means of which it is " locked," 

 and six " impulse " pins B near its arbor. The arbor carries a fly, not drawn. 

 The pendulum receives its impulse at each alternate beat ; at the beats from 



