In 1891 Professor A. H. Green wrote an interesting notice of two books, both of extreme value to the petrological student, viz. Cole's Aids in Practical Geology and Hatch's Introduction to the Study of Petrology. In the course of his review the Professor remarks: “In dealing with the foliated rocks, the author touches on the debated point of the ‘true schists.’ We are pretty well used to this phrase, and have waited long in the hopes of being told what constitutes a ‘true schist,’ but our patience has not yet met with the reward it merits. The author is of opinion that ‘the alleged distinction between schist-like rocks and schists of pre-Cambrian age requires great delicacy of definition.’ This is delicately put, and will command the assent of most geologists” (Nature, vol. xliv, p. 26).