This section is from "The Horticulturist, And Journal Of Rural Art And Rural Taste", by P. Barry, A. J. Downing, J. Jay Smith, Peter B. Mead, F. W. Woodward, Henry T. Williams. Also available from Amazon: Horticulturist and Journal of Rural Art and Rural Taste.
144. The object of this is, to remove leaves that shade the fruit so as to deprive it of the amount of light necessary to give it the proper flavor and color.
145. The leaves are taken off at several times. We ought not to commence uncovering the fruit until it is about to accomplish its maturity; that is to say, when the Peaches are nearly at their full size. They are not exposed all at once to the sun, as at Montreuil. The colder the season, the more leaves are taken off. It must not however, be forgotten, that an excessive defoliation may prove detrimental to the full development of the fruit; and that, at leaves are essential to the existence of the eyes, or buds, that grow from their axils, it is necessary to cut the leaf with the secateur, and to retain the petiole, and sometimes a third or half of the leaf, in order to preserve the embryo buds. It is also important not to take off any leaves from weakly shoots, the growth of which requires to be encouraged. Defoliation must be so performed as to assist the maturity and coloring of the fruit, taking care at the same time that it may not prove prejudicial to those young productions that should insure us future crops.