Richard Ketchum, of Seneca Castle, Onta-no Co., N. Y has taken measures to secure a patent for the following improvement in locks. The bolt is moved to and fro by a spindle, the end of which is bent at a right angle to the other part, or, in fact, forms a species of dog. When the door is locked it is the aim of the inventor to prevent this dog, which is thepart of the spindle brought to bear on the bolt, from being twned. This he effects by using a collar with a slot, a tumbler with a recess, and a plate likewise slotted ; all these three must, therefore, be adjusted to a certain position before the dog can be extricated. Secret marks or letters are also employed for further preventing of any tampering.