Magic Lantern Slides were gelatin on glass images produced between the Mid 1800 and the 1930's. The two most identifiable assists in dating these turn of the century images the drastic angle of leaning stone 56 which was straightened during the first period of restoration in 1901. It was about that time that the wooden props were installed. These wooden props were not removed until the second round of preservation work took place in the first half of the 1920's