[written on back of picture]: "This picture was taken in 1915 at Lyons, KS. This is a group of teachers from Rice Co., Ks. At this time this salt mine was the deepest one in the world. It was just at mile deep. This layer of salt was 15 ft. thick. One above it was 17 ft. thick. Salt rocks were blasted & "picked" - loaded in little steel cars - pulled by a single small mule, over a steel double rail to the elevators & taken up for processing into different uses - blocks for stock use, table, coarse for meat, rock salt for pickling & ice cream, etc. Black cord in forefront is electric cable. There was a time limit for keeping a mule in mine - had to be replaced by a new one. They were soon replaced by electric-fun cars."