Conserve of Sloes.
This may be made by boiling the sloes gently in water, being careful to take them out before they burst: afterwards expressing the juice, and beating it up with three times its weight of fine sugar.
In relaxations of the uvula and glands of the throat, this makes an excellent gargle, and may be used at discretion.
Preserves are made by steeping or boiling fresh vegetables first in water, and afterwards in syrup, or a solution of sugar. The subject is either preserved moist in the syrup, or taken out and dried, that the sugar may candy upon it. The last is the most useful method.
William Buchan
Domestic Medicine 2nd edition 1785