What is stockade?Deecribe the stockade or Treasure Island.Why is the spring important?

The standard deffinition of a stockade is a barrier formed from upright wooden posts or stakes, especially as a defense against attack or as a means of confining animals. The stockade in Treasure Island is a large blockhouse of logs equipped with firing ports surronded by a six-foot fence that has no opening. The sockade has a spring running through it. This is very important because they need a fresh water supply. 

The stockade is a sturdy logs cabin,with loopholes for muskets{guns} and was protected by a perimeter fence of stought wooden paling.

So,Captain smollet and many people of treasure island story considered this as an ideal{safe} place for them....