Complex sentence: The great effort failed; and four days afterwards Vergniaud and his whole party were further damaged by the discovery of a note signed by him along with Gaudet and Armand Gensonné and presented to the king two or three weeks before August 10.
Split into simpler sentences: The great effort failed; and four days afterwards something happened which still further endangered Vergniaud and his whole party. This was the discovery of a note signed by him along with Gaudet and Gensonné and presented to the king two or three weeks before August 10.