AMERICAN INSTITUTE. 535 



sider that the key was not used to lock or unlock it whilst he was 

 at work on it, which would not be the case when in use. 



This was picked by proving, or feeling, or as some call it the 

 tentative process trying. This operation requires a sensitive 

 finger, or fine sense of touch and feeling with the finger, and no 

 doubt if we should take 100 men who understood the lock as well 

 as Mr. Hobbs does, there would not be ten Who could feel out the 

 position of the slides, and be guided by their operations, and 

 probably not five who would have the patience to work sixteen 

 days to accomplish it. After this Bramah lock, Chubb attached to 

 the Barron tumblers a detective which was intended to be thrown 

 out of place if a false key was applied. This is considered by 

 some as a guide to pick the lock,- but it has done good service in 

 England. There are a good many in use in the United States. 



But it must be admitted that where great security is needed, a 

 lock with a fixed key, that always remains as it came from the 

 maker's hand, is liable to be imitated, or a duplicate kept by the 

 maker, who would then control the lock. This is an advantage 

 that is seldom taken, and goes far to establish the claim of the 

 lock-makers to a high degree of hone&ty, when we take into con- 

 sideration the temptations they meet with. 



Keys that could be taken to pieces were made in England years 

 ago, and afterwards locks were made so that they could be taken 

 apart and changed. This was a great improvement, as it allowed 

 a new lock to be made as often as the changes lasted, with very 

 little trouble, and no doubt a lock that can be changed by hand 

 is sufiiciently convenient for ordinary purposes, as you have great 

 advantages at the expense of a little time spent in changing the 

 lock and key. This has been accomplished in a great many 

 forms in locks with keys, also in compensating locks without 

 keys. 



Considering the advantages of changing a lock, it must be ad- 

 mitted that there is greater advantage in a lock that is self- 

 changing, or one that will change without the necessity of taking 

 it apart. This was accomplished first in the United States, and 

 at the time admitted to be an improvement over all others. In 

 this case there was but one set of tumblers used, and the change 



