"Also I found some tid-bits in the O.R. I had missed. When Anderson's mail was stopped in the days prior to April 12th, apparently the Fox's plan was discovered in a message to Anderson."

From "fighting For the Confederacy" by Gen. E. P. Alexander page 29
"But meanwhile a fleet of transports & war vessels was prepared in New York to reinforce the garrison at Fort Sumter and after it set sail for that purpose Seward notified So. Ca's representatives of the fact,& as I recollect with an apologetic explanation (which practically admitted that it was a violation of his pledge)that he had been unable to prevent it."

GP