Coppee.] 158 [March. 



the mercury to the other pole of the battery. Thus at every swing 

 of the pendulum the circuit was made, and a suitable apparatus 

 might, by the electro-magnet, record each alternate second of time. 



'' The amount of power requii-ed of the pendulum to give motion 

 to the delicate wire-cross was almost insensible, as the stems nearly 

 counterpoised each other in every position. Here, however, there 

 was great difficulty in procuring a fibre sufficiently minute and elastic 

 to constitute the physical union between the top stem of the cross 

 and the clock pendulum. Various materials were tried, among 

 others a delicate human hair, the very finest that could be obtained, 

 but this was too coarse and stiff. Its want of pliancy and elasticity 

 gave to the minute 'wire-cross' an irregular motion, and caused it 

 to rebound from the globule of mercury into which it should have 

 plunged. After many fruitless efforts, an appeal was made to an 

 artisan of wonderful dexterity; the assistance of the spider was in- 

 voked. His web, perfectly elastic and perfectly pliable, was fur- 

 nished, and this material connection between the wire-cross and the 

 clock pendulum proved to be exactly the thing required. In proof 

 of this remark, I need only state the flict that one single spider's 

 web has fulfilled the delicate duty of moving the wire-cross, lifting 

 it, and again permitting it to dip into the mercury every second of 

 time for a period of more than three years ! How much longer it 

 might have faithfully performed the same service I know not, as 

 it then became necessary to break this admirable bond, to make 

 some changes in the clock. Here it will be seen the same web was 

 expanded and contracted each second during this whole period, and 

 yet never, so far as could be observed, lost any portion of its elasti- 

 city. The clock was thus made to close the electric circuit in the 

 most perfect manner; and inasmuch as the resistance opposed to the 

 pendulum by the 'wire-cross' was a constant quantity and very 

 minute, thus acting precisely as does the resistance of the atmo- 

 sphere, the clock, once regulated with the ' cross' as a portion of its 

 machinery, moved with its wonted steadiness and uniformity. Thus 

 one grand point was gained. The clock was now ready to record its 

 own beats automatically and with absolute certainty, without in any 

 way affecting the regularity of its movement. It was early objected 

 to the mercurial connection just described, that in a short time the 

 surface of the mercury would become oxydized, and thus refuse to 

 transmit the current of electricity; but experiment demonstrated 

 that the explosion produced by the electric discharge at every dip 

 into the mercury threw off the oxyd formed, and left the polished 



