372 n purifying Olive Oil j 6r 



to be able to lay before the commissioners a more detailed 

 analysis, containing a minute examination of the compo- 

 sition of the ashes contained in the charcoal, and also the 

 exact composition of the gaseous products." 



LXVII. On purifying Olive Oil for the Pivots of Chro- 

 nometers, By Ez. Walker, Esq. 



To Mr. Tilloch. 



Sir, After all the experiments which have been made 

 to decrease friction in time-keepers, nothing has yet been 

 found to answer this purpose so well as oi!. But it has 

 long been known that the application of this fluid to ma- 

 rine chronometers is attended with very pernicious conse- 

 quences ; for it gradually loses its fluidity during a long voy- 

 age, and adheres to the parts of the machine, by which all 

 regularity in its performance is destroyed. Hence I was 

 led to suppose, that time-keepers might be improved if oil 

 of a better quality, than that which had been commonly 

 used, could be procured. 



About the year 1799? I made several experiments to se- 

 parate from olive oil some of those impurities which it is 

 known to contain, and I succeeded so far as to separate a 

 thick mucilaginous matter from the best I could procure. 

 This mucilage is an opake whitish matter, heavier than oil 

 but lighter than water. The oil from which the mucilage 

 has been taken is exceedingly transparent in a fluid state, 

 but after it has been frozen it appears much whiter than 

 common oil exposed to the same degree of cold. 



About ten years ago I sent a small quantity of this oil to 

 Mr. Barraud, requesting him to make trial of it, and to 

 March 1802 he gave me the following account: — 



" I have," says Mr. Barraud, "just received a chrono- 

 meter, in which the oil you favoured me with was used ; 

 which having performed a voyage of 16 months to and from 

 India, is vibrating as freely as at first, and keeping the rate 

 it went out with to a fraction of a second. " 



Since that time Mr. Barraud has frequently applied to 

 me for more of this oil, and continues to use it in his best 

 time-keepers; but to be informed more particularly respect- 

 ing it, I wrote to him requesting to know the result of his 

 long experience, and the following extract is taken from his 

 interesting answer : — 



"To 



