Mr Sang on the Effect of Friction on Time-Keepers. 129 



Explanation of Plate II L 



Fig. 1. Right half of the head of a Rabbit. 



a. Inferior turbinated bone. The direction of the currents is indicated 



br the arrows. 

 h. Superior turbinated bone, 

 f. c. Palate. 

 d. Tongue, 

 ft Pharynx. 

 /. Epiglottis and opening of the larynx. 



Figs. 2 and 3 are from the Newt ; Figs. 3 and 4 from the Toad. The letters 

 refer to the same parts in both. On the accompanying outline*? of which 

 that in Fig. 3 is enlarged, the arrows indicate the situation and direction of 

 the currents. 



a. a. Lower jaw detached from the upper. 



h. Tongue. 



c. Glottis. 



d. Gullet cut off from the head (at g. g. Figs. 3 and 5), and laid open 



above. 



e. Stomach. 

 /./. Lungs. 



Figs. 3 and 5 represent the head and roof of the mouth, from which the 

 lower jaw has been separated. 



g. g. Cut edge of the membrane where the pharynx and gullet were 



detached. 

 h. h. Nostrils. 



On the Manner in which Friction affects the Motio?is of Time- 

 Keepers. By Edward Sang, Esq., Teacher of Mathematics, 

 Edinburgh, Member of the Society of Arts, &c. Communi- 

 cated by the Author. 



In the usual method for determining the length of the seconds 

 pendulum, the effect of friction is allowed to accumulate until 

 a great part of the motion is destroyed. Yet no regular inves- 

 tigation, that I know of, has ever been given of the influence 

 which this circumstance must e.\ert upon the final result. The 

 measurement of the length of the pendulum throws great light 

 on one of the most difficult questions of physical astronomy, 

 and at the same time furnishes a distinct standard to which the 



VOL. XIX. XO. XXXVII JULY 1835. I 



