Wash and pick over berries and dice rhubarb. Put fruit in kettle with pinch of soda and just enough water to cover. Cook slowly until the fruit is soft and tender and then strain through a cotton flannel bag. Add an equal amount of sugar to the strained juice, bring the boiling point and simmer gently until it jells. A good plan is to see if the last drop on the spoon can be held while counting sixty, as then it will surely jell. Pour into hot sterilized glasses, cool and seal.