Bascom Lake, the tremendous body of water which lapped the sides of Mt. Greylock thousands of years ago, is being immortalized in fresco on the walls of the mineral room of the Berkshire Museum.
Within the three round-topped window frames on the east side of the room, William Melton Halsey, young Boston Museum of Fine Arts student and instructor, is reconstructing the Greylock region as it looked when the great glacier departed and the Berkshires began to emerge from their shroud of ice.
The upper half of the completed mural will show Greylock and the lake in perspective. The lower portion will cut the panorama in cross-section to show the geologic makeup of the region. Each of the strata which has been built up in the countless years since the Ice Age will be indicated and labelled.
The surface of the great lake, as visualized by geologists, was 1,700 feet above sea level, some 1,800 feet from the present summit of Greylock. Its waters were 500 feet deep where the town of Adams now stands. The sites of both North Adams and Williamstown were far under water, which stretched northward to the foothills of the Green Mountains.
The fresco method of painting, little used in recent years until stimulated by Federal Art Projects, is the primary reason for the survival of the great works of Leonardo da Vinci and Michelangelo. It is the most time-resistive of all painting methods, being capable of lasting an estimated 1,000 years.
The secret of fresco's longevity is that it is painted on wet plaster. The artist uses ordinary pigment mixed with water. The mixture sinks into the wet plaster, receives a warm chemical welcome from the lime in the plaster and thus becomes a part of the surface instead of just a coating on it.
As befits its life expectancy, fresco requires a long period of preparation. At least a month before the painting is to be done, the first three coats of plaster must be put on. These build up to almost three-quarters of an inch. The surface plaster is put on to a depth of about a quarter of an inch, and only as much is put on at one time as can be painted in a day.
Mr. Halsey was painting in Charleston when Miss Laura M. Bragg, Berkshire Museum director, was serving as director at the Charleston Museum.