400. That’s an error.

Google cannot redirect you to http://worldcat.org/search?q=history+England,+invasion+Julius+Cæsar+revolution+1688.+5+vols.+[in+9.+plates+dated+1797+1806].+david+hume because the request was invalid.

This might be because the link was created a long time ago. Try your search again on Google. That’s all we know.