348 



NATURE 



\August 7, 1879 



Pi through the angle b^, the tooth / has allowed the 

 springs to drop, and that it travels through its correspond- 

 ing angle b perfectly undisturbed. The motion of the 

 tooth /j can easily be traced from the drawing. Careful 

 workmanship is required to carry out this method pro- 

 perly, as the angles a, a^, a^ ought to be made much 

 smaller than in the drawing. 



Fig. 8 shows some electrical dial work. 



M M are coils, A A is an armature, L L a lever turning 

 about C. D D is mounted on L L and kept in position by 

 a spring. J j is a jumper. As soon as a current ceases, 

 L L, which has been attracted by M M, falls, and D D 

 drives forward a tooth, Xj. When D d reaches the limit 

 of its thrust, the point of jj just gets round the corner of 

 Tj, and drives on Tj, makes it jump a little further. The 

 jumper seems a better arrangement than the usual 

 ratchet. 



Fig. 10. 



It has become popular of late to set the hands of indif- 

 ferent clocks by electricity. This plan was proposed by 

 Mr. Bain as far back as 1843, and his method of accom- 

 plishing it was as follows (see Fig. 9). Behind the minute 

 hand at 12 o'clock is placed a V, and in the minute hand 

 is a pin. Every hour a current from the standard clock 

 raises the V. Should the hand be fast or slow it is imme- 

 diately forced to the hour, for the pin is bound to find its 

 position at the bottom of the V. A plan similar in opera- 

 tion has recently been patented by Messrs. Barraud and 

 Lund. It is fully described in Nature, vol. xix. p. 55. 



Another method of correcting clocks was invented by 

 M. Collin, Chevalier of the Legion of Honour, and has 

 been largely made use of by him. Fig. 10 shows his 

 standard clock, and Fig. 1 1 the clock to be corrected ; 

 the latter is regulated to gain a second or two per hour. 

 A few minutes before each hour the lower of the two 

 detents in Fig. 10 is lifted against the upper, and a current 



passes. As regards the clock, Fig. 11, the current avoids 



Fig. II 



for the present the coil mounted on the top of it. When 



Fig. 12. 



the clock. Fig. 11, reaches the hour, it allows the long 



