of minute Forces on the Rate of the Seconds Pendulum. 439 



No. 12, as compared with those of No. 1 1, is accounted for. 

 If T5 second be allowed for the difference in the extents' of 

 vibration, and if to this the 1 second actually shown by expe- 

 riment be added, the amount 2\5 seconds will be the difference 

 between the two methods, — the one of giving the whole of the 

 impulse in ascent, and the other of giving three fourths of it 

 in descent. 



When the pendulum was suspended by a strong adjusted 

 spring, there was no less than 5 seconds of difference between 

 the results of the two methods. 



In consequence of this alteration on the pallets, the pendu- 

 lum had been lengthened so as to produce a difference of 4? or 

 5 seconds in 24? hours, which accounts for so great a difference 

 in time as that shown between the experiments of Nos.10 & 1 1. 



Set, No. 13. — With the same pendulum bob as before, the 

 impulse being given equally in ascent and descent. 



,-, . . Gain in Extent of 



Experiments. 24 Hours. Vibration. 



In air -f-12-7 3 1*8° 



Ditto +12-6 1-8 



In exhaustion, 6 in. . . +18*0 2*06 



Ditto 14 . . . +16-3 1-9 



In air +13*0 1-8 



Ditto +12-5 1-8 



Set, No. 14. — With a round bob of 8 pounds 2 ounces in 

 weight, the impulse being given in the middle. 



i? v »^', mon *.« Gain in Extent of 



Experiments. 24 Hours. Vibration. 



In air + 4'6 S 1*43° 



Ditto +4-8 1-43 



In exhaustion, 6 in. . +14*6 1*8 



Ditto 13-5 . . +13-5 1-6 



In air +4-8 ....... 1*43 



Set, No. 15. — With the pendulum vibrating on a knife-edge, 

 and the same maintaining power as above. 



v . Gain in Extent of 



Experiments. 2 4 Hours. Vibration. 



In air + 4-1 8 1-58° 



Ditto . +4-7 1-58 



The comparison of these experiments with the preceding, 

 shows the increase in. the extent of vibration arising from the 

 substitution of the knife-edge for the suspending spring; or in 

 other words, the loss in the extent of vibration arising from the 



