On Oil and Oil-gas. 65 
at about 400° of Fahrenheit. After this it 
begins to exhalea vapour, which is chiefly 
aqueous; and this continues for some time. 
When the temperature arrives at the confines 
of 600°, symptoms of ebullition begin to ap- 
pear, by a number of small bubbles of air and 
vapour emerging from the surface of the oil. 
The heat being continued, the teniperature 
‘gradually increases from 600 to 650° or up- 
wards, when the whole surface has a very 
gentle curlor agitation, which continues with- 
out much change as long as the temperature 
is kept between the limits of 650° to perhaps 
700°. The higher limit is not very easily 
ascertained, by reason of the mercurial ther- 
mometer ceasing to be a measure of temper- 
ature at that extreme. There is a striking 
contrast between the violent agitation of wa- 
ter and the gentle agitation of oil, in a state 
of ebullition. When a quantity of whale 
oil, is subjected to distillation in a glass retort, 
it may be gradually heated to 500° or up- 
wards, at which time a little water and oil 
will have distilled over, amounting to 4, or 
<> of the whole. This being withdrawn and 
another receiver placed, a portion of oil will 
be distilled, mixed with a little water, when 
the temperature reaches 600°. Ebullition 
having commenced, the distillation quickens 
I 
