is that while it will mark a piece of paper in a greasy fashion, the mark is not permanent, but will in a certain time entirely disappear, and, under the influence of heat, disappear more rapidly.
They have the property, as have certain other oils, of becoming solidified and leaving a deposit of rosin.
Technically, there are many varieties of these oils, which are all duly classified, but for our purpose we can divide them into two broad classes–those that remain liquid and those that can be solidified in the form of crystals.
They are hardly soluble in water, though they impart to it its odour.
NOTE. I have throughout used the word drying, because it is the usual expression. As a matter of fact oil does not dry at all, but becomes solid by contact with the oxygen in the air, and clings permanently to the surface to which it is applied.
