Cut the cantaloupe in half. Remove the seeds and stringy fibers, scoop out the pulp with a large spoon and chop it coarsely/ Wash the strawberries and grapes under cold running water, picking out and discarding any fruits that are badly bruised. Remove and discard the stems. Combine the cantaloupe, strawberries, grapes, apples, half cup of the lemon juice, the sugar and water in a 4 to 6 litre enameled or stainless steel saucepan. Bring to a boil over high heat, reduce the heat to low and simmer uncovered for 15 minutes. Puree the soup through a food mill, or pour the entire contents of the pan into a large fine sieve set over a deep bowl and force the ingredients through with the back of a spoon, pressing down hard on the fruits before discarding any remaining pulp. Stir the remaining quarter cup of lemon juice and the orange juice into the soup and refrigerate for at least 2 hours, or until thoroughly chilled.