Foundation within a foundation

After Martin removed the joists from the kitchen addition, he dug out and removed most of the bricks that were the base of the chimney (he only stopped because he was running out of support post and didn't want to have that section of the wall collapse).  In the process of digging it became obvious that there was the remnants of a fieldstone foundation, which is not the full length of the house and narrower than the most recent addition.  Part of the foundation was incorporated into the back wall of the kitchen addition and part of the foundation is under the original outside wall of the house.  Our best guess is, that at some time after the original house was built, an addition was put on. The water line comes into the house within this older foundation, so this might have been the original kitchen addition (that was expanded at some later date) and put on to incorporate the new water line, or this might have been the original kitchen foundation and the owners decided to have the running water piped into it.