Todd,
You are correct. According to the 1913 C&S Rwy. Tie and Timber Specifications, narrow gauge ties were to be 6" thick x 6" on the face x 6' 6" long. They could be 1/2" thicker and along the face, and 1" shorter than specified. They were to be made from Red Spruce or Yellow Pine. No White Pine, White Spruce, or Balsam Fir were to be used.
Doug
Doug Heitkamp
Centennial, CO