400. That’s an error.

Google cannot redirect you to http://www.ampere.cnrs.fr/correspondance/corr_ampere_affi_lettre.php?lang=en&table=ampere_corr_main&bookId=942&exp=Faraday, Michael&dest=Ampère, André-Marie 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.