The house was built in the 50's, but when was the linoleum flooring installed in the kitchen?
If this is still the original flooring in the kitchen, then I'd suspect the problem is simply that after 50 years, the vinyl wear layer is separating from the paper backing, and the result looks like "bubbles". Basically, your linoleum floor is at the end of it's useful life.
If I were you, I'd simply phone up any of the carpet retailers in your area (all of whom both sell and install other kinds of flooring) and ask if they can have one of the most knowledgable installers take a look at it in person. I very much doubt they'd charge you anything just to look at it and give an opinion on what else it might be.
