Extract
The rocks exposed along the road between Linstead and Guy's Hill, Jamaica, were described by Dr. C. T. Trechmann in this magazine in 1936 (pp. 259–260). The chief object of his account was to prove that the igneous rocks there were intrusions later than the associated Cretaceous and Tertiary limestones, which, according to him, had been metamorphosed into hornfelses, some of which, he stated later (1937, p. 561), he knew to have an “igneous” appearance under the microscope, “which tends to support my contention that in Jamaica we have sedimentaries altered in situ into rocks that would ordinarily be classified as igneous.” Dissent from his descriptions and interpretations was expressed by C. A. M. (Matley, 1937, pp. 501–3), the criticisms being mainly based on an examination of Trechmann's own microscope slides by F. R. A visit to Jamaica by C. A. M. in 1939 allowed him to study this road and to collect a suite of rocks for petrological examination. The results show that Trechmann's interpretation cannot be sustained. There is no granodiorite or other plutonic rock present, no metamorphism hornfelsing the sedimentary rocks, and no igneous intrusions into the Tertiary limestones.