Note Footnote 9: — Chapter II
Reading edition
The hardness of wood is of much consequence in gluing pieces together. Soft woods, like pine, can be glued easily, because the fibers can be forced close together. As a matter of fact, the joint when dry is stronger than the rest of the board. In gluing hard woods, however, it is necessary to scratch the surfaces to be glued in order to insure a strong joint. It is for the same reason that a joint made with liquid glue is safe on soft wood when it would be weak on hard wood.9