John Phillip Holland and his submarines - website

 Excellent website on the Holland boats and some information on Holland himself.  Reviews the various boats with a nice amount of information on the Holland VI with original Navy and yard documents, trial logs, illustrations and Holland patent listings.

Good technical details on the systems and operation of the Holland VI.  Water and air system diagrams, and a description of the ballast and propulsion systems.  It's not enough information to build a full-scale copy of this 100 year old sub but you could use it for a model.

Also covers competitors and variants of the Holland VI built in other countries.

Website link