204 On correcting the Rate of an Electric Clock. 



tirm of the balance which carries the clock. Two flat plates of 

 brass (four inches long and one inch in breadth) insulated and 

 connected with the opposite extremities of the columns are 

 placed at such distances, viz. about one inch from the ball of 

 the pendulum, which is also insulated, that it vibrates between 

 them by the joint forces of gravitation and electric attraction in 

 half seconds; and they are inclined to such angles with the 

 pendulum, that the degree of heat, which causes the columns to 

 act more powerfully, at the same time, by expanding the spirit, 

 raises the piston, the beam, and the pendulum into a position 

 where the vibrations of the latter are proportionally longer ; and 

 consequently, these two different effects of heat are thus made 

 to compensate each other; and the instrument actuallv keeps to- 

 lerably good time : — how long it will continue to do so, must 

 depend upon the constancy of the columns. But the regularity 

 and steadiness of the vibrations are also much improved by en- 

 veloping the columns in cement, which was laid on in a liquid 

 state,so that no moisture can be driven out of the squares of pa- 

 per, and by the ball or bob (which is of brass, with a fine gold 

 girth,) being very considerably heavier than those of cork or thiu 

 ailver which I had hitherto employed. 



I believe the principal defects are now those arising from a 

 difference between the rates of heating and cooling of the spirit 

 thermometer and the columns, and from some unknown circum- 

 stance whicl\ has been attributed to the electric state of the 

 ambient air. The larger the seiies employed, and the heavier 

 the pendulum, the more correctly it seems to vibrate*. 



Amongst other interesting intelligence from your learned cor- 

 respondent M, Van Mons, it appears that Sign. Zamboni has 

 been enabled to produce strong sparks and shocks by the co- 

 lumn, the construction of which he seems to have thus very 

 greatly improved. With the help of a condenser I have advan- 

 tageously substituted it for the electrojjhorus in Volta's inflam- 

 mable air-lamp, which is apt to get out of order; but Sign. Zam- 

 boni's columns could be used without this assistance. 

 I remain, sir. 



Your obliged and humble servant. 

 Hammersmith, Sept. 15, 1815. FraNCIS RonalDS. 



• As Mr. Singer's account of theiiucntiun of this iiibtniment seemed very 

 inconsistent with mine, 1 wished it to he clearly iiiiilerstood, for the infor- 

 mation of his friend in the note to wliieh he Inis referretl, tliat I derived 

 no kind or' supge.tion from any person whatever respecting the employ- 

 ment of an inriexihle penduhim. That Mr. Singer shoukt hoiionr inc with 

 the title of his pupil, I certainly did not at all expect. The other facts 

 stated in that note can be verified without difficulty, by any who may think 

 them of sufficient consequence to repeat the experiments upon which they 

 are founded. 



XXXVII. On 



