156 TRAXSACTIONS OF THE [fEB. 15, 



vantage of this form, invented by Mr. C. H. Pontl, of New York 

 City, is that it can be attached to many forms of ordinary 

 clocks, and can also be adapted to the more delicate clocks used 

 in the observatories. As to how constant a rate an astronomical 

 clock would have when provided with such a winding ajiparatus 

 and impelled by a spring instead of by weights, we cannot say. 

 We hope to be able soon to make some ex})eriments on the rate 

 of a fine clock provided with this new apparatus. Such an ar- 

 rangement of apparatus could be put into an hermetically 

 sealed case and phiced in a room with a fixed temperature, and 

 be beyond the reacli of both variations of rate due to temperature, 

 and those due to barometric pressure and to moisture. 



Tiie inventor claims that tlie electro-mechanical clock has the 

 following advantages over the ordinary weight or spring clock as 

 made hitherto: 



1. The friction and wearing parts are reduced to a minimum. 



2. The winding is so arranged that a uniform tension is kept 

 on the train during the process of winding. 



3. A given force or propelling power exerted on the hour arbor 

 actuates tlie escape- wheel with a large per cent more force than 

 is attained in the ordinary clock driven in the ordinary way. 



These advantages are secured in the following way: The wheels 

 and arbors below the hour or centre arbor are removed from the 

 clock. In their place a small electric motor is substituted. 'J'his 

 little motor connects with a spring barrel on the centre arbor, 

 which incloses a spring six feet long and three-sixteenths of an 

 inch in width and six-one-tliousandths of an inch in thickness. 

 This spring at its inner end is attached to the arbor, and at 

 the outer end to the periphery of the spring barrel. The spring 

 is wound aronnd the arbor a great many times, but not wound 

 so close as to produce friction between the coils; and being at- 

 tached to the hour arbor, it follows that the inner end will unwind 

 one turn in one hour. By a simple attachment the electric 

 circuit is made to pass into the motor already referred to, which 

 quickly aiid silently carries the spring barrel around once (being 

 loose on the shaft), and the outer end of the spring attached to 

 its periphery with it. Upon the completion of the revolution of 

 the spring barrel, as described, the electric circuit is broken and 

 the motor stops. By this arrangement, it will be observed tliat 

 the inner end of the spring always has a motion from left to right, 

 or in the direction of the hands' motion, and the outer end of 

 the spring a motion in the same direction, each hour. 



Now, since the winding is done in the same direction as the 

 unwinding of the inner eml, and the spring is so wound originally 

 as to avoid friction between the convolutions, it follows that the 

 tension upon the train is absolutely uniform at all times, whether 



