188 
On purifying Olive Oil for 
yet been found to answer tliis purpose so well as oiL 
But it lias long been known that the application of this 
fluid to marine chronometers is attended with very perni- 
cious consequences : for it gradually loses its fluidity 
during a long voyage, 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 pro- 
cured. 
About the year 1799, I made several experiments to 
separate from olive oil some of those impurities which it 
is known to contain, and I succeeded so far as to sepa- 
rate 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 trans- 
parent in a fluid state, but after it has been frozen it ap- 
pears much whiter thaij 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 in March, 1803, he gave me the following ac- 
count:— 
“I have,” says Mr. Barraud, “just received a chro- 
nometer, in which the oil you favoured me with was 
used ; which having performed a voyage of sixteen 
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 
respecting it, I wrote to him requesting to know the re- 
