After Martley’s work a small number of authors investigated growth stresses through the 30’s and 40’s. \citet{jacobs1945l}, testing 34 hardwood species, focused mainly on Eucalyptus and argued that (longitudinal) tension successively develops in the outer layers of the stem as it grows, and as a consequence of the tension, compression must form in the centre of the stem. Experimentally Jacobs made use of strip planking, measuring the deflection of the board after removal from the log, and the length change when the planks were forced back straight. He showed that wood tends to shrink in the longitudinal direction at the periphery while extend near the pith (indicating the log is under compression in the centre and tension at the extremities).