1928. Drummond's valve mole-trap (fig. 524.) is a very simple and useful contrivance. The mole entering at a b is prevented from returning by the valve c, which is made of such a length and placed in such a position as to admit of its opening inwardly only; and from the narrowing of the hole the animal cannot turn itself. The valve on a larger scale is shown at c and the pin on which it moves at e d, the pin being fixed into the tube at f g.