244 Mr. Scrymgeour's Experiments to determine the Influence 



the fact of the irruption of the sea by destroying the ancient 

 dykes, nor with regard to the period which they assign as the 

 date of that event*. 



XL. Narrative of Experiments made with the Seconds Pen- 

 dulum, principally in order to determine the hitherto un~ 

 assigned Amount of the Influence of certain minute Forces on 

 its Rale of Motion, By Mr. James ScRYMGEouRf. 



HPHE author's object in making the experiments detailed in 

 ■* the following narrative, was so much ramified in the course 

 of his researches, that it will be best understood after their 

 perusal. 



Suffice it at present to say, that he had in view to ascertain 

 the influence of the maintaining power, or escapement on the 

 time of the vibrations of the pendulum in which no recoil is 

 produced ; and likewise the effect of the resistance of the air 

 upon the vibrations, either when the pendulum is attached to 

 a clock, or when it is in a detached state. 



The results of these experimental researches will be found 

 applicable to all the contrivances or escapements for giving the 

 impulse to the pendulum without recoil. As recoil was con- 

 sidered to introduce sources of irregularity, it was deemed 

 unnecessary to inquire into its effects, as they would be inde- 

 finite and would vary with the quantity of recoil; besides, such 

 experiments would be applicable to the clock employed only. 



In pursuing this inquiry, my first object was to make the 

 suspending spring of two of my clocks (which had both dead 

 escapements) such as to cause the long and short vibrations to 

 be performed in equal times. For this purpose, I shortened 

 the acting part of the suspending spring of one of them, which, 

 for the sake of distinction, I shall call my shop time-piece. 

 This clock has a common lenticular bob with a wooden rod ; 

 it had been going for five or six years previously, with the sus- 

 pending spring made in the usual way, of a piece of middle- 

 sized watch main-spring about j of an inch in length. The 

 bob is only about 4 pounds in weight, with a small brass ball 

 below it, nearly J of a pound in weight. 



The action of the suspending spring was shortened by 

 fixing a piece of steel on each side of the spring, and joining 

 it to the rod, so as to reduce the acting part of the spring to 



* See the Cambro-Briton, for Jane 1820, vol. i. p. 361 ; Edward Wil- 

 liams's Lyric Poems, vol. i. p. 78. note ; Davies's Mythology and Rites of 

 the Druids, p. 240, &c. ; Meyrick's Hist, and Antiquities of the County of 

 Cardigan, p. 50 — 80. t Communicated by the Author. 



