248 Description of an improved Drawback Lock. 



nucleus, or centre of the charges^ a solid body*, a vacuity 

 or vessel filled with any liquid. Some trials made with a 

 six-pounder gave us results capable of exciting attention, 

 and which will induce me soon to resume them. 



XLIV. Description of an improved Drauhack Lock for 

 House Doors, invented by Mr. William Bullock, of 

 Portland-street \. 



SIR, 



X HAVE herewith sent, for the inspection of the society^ 

 an improved drawback lock for house doors. Sec. which 

 improvement is in latching tjie door; for iLis well known-, 

 particularly in damp weather, that the air drawing through 

 it rusts the head or bevel of the bolt, by which means it 

 requires great force to shut the door, and occasions a dis-r 

 agreeable noise, besides shaking the building. 



It has frequently happened that the house has been ex- 

 posed to robbery from the door being left unlatched, when 

 supposed to be fast. This improvement removes all those 

 inconveniences, as it lets the bolt shoot into the staple 

 immediately when the door closes, but not before ; and the 

 reliever works so very easy, that the door is made fast with 

 one twenty-fourth part of the force required with locks upor^ 

 the common construction. 



By an experiment with the lock sent herewith, it will be 

 proved that two ounces added to the rehever, will shoot 

 the lock wiih more ease than three pounds will do applied 

 to the bevel bolt ; and if the lock is rusty, the advantage 

 will be much more in favour of the new method. I flatter 

 myself it will be of great utility to the public, as its con- 

 struction is simple -and cheap. It may be added to any olcj 

 lock, as may be seen from that now sent. It may be ad- 

 vantageously applied to French windows and glass doors, 

 as it prevents the door from being strained, or the glass 

 broke, by the "^brce applied to shut them. I have fixed 

 several locks upon this new principle^ which answer well ^ 



• This, it is said, is already practised, with advantage, by some Ger-. 

 man mintrs. 



•}• From Transactions of the Sccicij of Arts, iic. vol. xix A bounty 



pf fifteen guineas was voted to Mr. Bullock for this communication. 



H 



