400. That’s an error.

Google cannot redirect you to http://worldcat.org/search?q=Opuscules,+mathematiques+ou+memoires+sur+differens+sujets+Geometrie+mechanique+etc+jean+le-rond+d'alembert 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.