In 1860, the number of students in Arts, Law and Science had increased to one hundred and five, of whom sixty were in Arts. It had been previously decided that when the students in Arts should exceed fifty, the original College buildings should again be wholly occupied. They had meanwhile undergone extensive repairs. The College grounds were now taking on some semblance of order as a result of trees and walks and clearings. Accordingly, in the autumn of 1860 the classes in Arts, Science and Law were moved back to the buildings which had been practically abandoned eight years before. The centre building was used for classes; the east wing was given up to rooms for the Principal and some of the professors and students. The erection of a third building, corresponding with the east wing, was then undertaken through the generosity of William Molson. It provided for a convocation hall above, and a library below. It was formally opened in 1862, and is known as the William Molson Hall. Through the efforts of Mrs. Molson the three buildings were soon afterwards connected into one, by intervening structures, and the Arts building as we know it was completed. One of the connecting structures was used first as a museum; the other as a Chemical and Natural Science room and laboratory. The museum received at once a portion of the Principal's own collection of specimens, and others purchased by the Principal from his own resources. Later Dr. Carpenter's valuable collection of shells was added, and the whole furnished the nucleus for the present Peter Redpath Museum. The Science room and laboratory were used for chemistry and assaying. It was there, in small rooms and with but scanty equipment, that Dr. Harrington later laid the foundations for the departments of Chemistry and Mining which were subsequently to contribute so largely to the industrial development of Canada. The Library in Molson Hall had room for twenty thousand volumes, but when it was opened the College possessed only two thousand books. These, however, formed the nucleus for the Peter Redpath Library.