Do research papers have a Public Domain Expiration Date? simmilar of what happens to literature books
For example, let's consider a research paper of James C. Maxwell: XVIII.—Experiments on Colour, as perceived by the Eye, with Remarks on Colour-Blindness, it is stored in here: link to www.cambridge.org website
It says: "Copyright © Royal Society of Edinburgh 1857" and if I want to purchase the article, it would cost me: USD35
This is an article published more than 150 years ago. How long do I have to wait in order to download it and use it for free?