In an earlier paper( Karrick and Lewis) A convenient and reliable retort for assaying oil shale for oil yield: Bureau of Mines Reports of Investigation, serial no. 2289 March 1921. Reprinted in Eng.. and Min. Jour. April 30, 1921, also in Mining and Met. May 1921, which describes the apparatus and method used in the laboratories of the Bureau of Mines for assaying oil shales, no mention is made of the quality of oil obtained when the apparatus is operated under conditions determined to be most suitable for producing highest yields of oils. So many inquiries regarding the nature of the oil have been received that it seems advisable to present a short report on the subject.