Allow 3/4 lb. of white sugar to 1 lb. of fruit. It is difficult to give the exact quantity of sugar to be used in plum jam; in fact, it entirely depends upon the quality of the plums used; therefore your own judgment will be necessary. After weighing the plums halve them and remove the stones; then place on a large dish and sprinkle with the sugar; leave them thus for 24 hours; then put into a preserving-pan and let them simmer gently on the back of the stove for about 25 or 30 minutes, then boil very quickly for 1/4 hour, skimming carefully, and stirring with a wooden spoon to prevent the jam sticking. It greatly improves the jam to put some kernels from the plum stones into it.