On Variations in the Vibrations of Pendulums. 59 J 



2. All of these poisons occasion disorder of the functions, 

 of the heart, brain, and aHnientary canal ; but they do not 

 all affect these organs in ih?? same relative dej^ree. 



3. Arsenic operates on the alimentary canal in a greater 

 degree than either ihc emetic tartar, or the muriate of 

 barytes. The heart is afiecied more by arsenic than by the 

 emetic tartar, and more by this last than by the muriate of 

 barytes. 



4. The corrosive subiimate, when taken internally in 

 large quantity, occasions death by acting chemically on the 

 mucous membrane of the ston)ach, so as to destroy its 

 texture; the organs more inimediaielv necessary to life 

 being affected in consequence of their sympathy with the 

 stomach. 



Tn making the comparison between them, we observe 

 that the effects of mineral are less simple than those of the 

 generality of vegetable poisons; and when once an animal 

 is affected by the former, there is much less chance of his 

 recovery than when he is affected by the latter. 



XLIX. On Variations i?i the Vibrations of Pendulums. By 

 Ez. Walker, jE^^. 



To Mr. Tillocfi. 



Sir, /jl letter from Mr. Thomas Reid, of Edinburgh, 

 published in the Philosophical Journal, No. 152, gives an 

 account of his observations on the effect of the attraction 

 between the weight and the pendulum on the going of 

 clocks. 



Mr. Reid obi^erves, that " it will perhaps be thought 

 strange to say, that attraction comes in for a share in those 

 obstacles which stand in the way of good time-keepina;. 

 'J'his is what has never been even hinted at before; if it 

 has, I confess it is new to me." 



Mr. R. fitted up u clock to go a month or six weeks, 

 which he expected to keep the arc of vibration of 

 the pendulum as nearly constant as possible ; but after 

 keeping this arc perfectly for above two weeks, it surprised 

 him to find that it began to diminish its arc, and after a 

 tune to increase again. This variation in the arc of vibra- 

 tion he wa» convinced " must arise from the attraction of 

 liie weight lor the pendulum." 



This variation in the arc of vibration, in clocks which 



CO a month or more, is not a new discovcrv, for it has 



liccii known to me more than thirty years. My clock goes 



T 3 a month 



