Peaches contain so little pectin that it is almost impossible to make jelly of them unless some other fruit is added in rather large quantities. Currants, crab apples, or green grapes may be used with peaches, and whichever one is selected will be needed in the proportion of about 50 per cent.; that is, half as much additional fruit as peaches is needed. In the making of peach jelly, proceed as for currant jelly.
Woman's Institute Library of Cookery, Volume 5.