Not sure if this will be helpfull or not but the law systems use the word current is the same as electrical current is taken from the Law of the Sea current... in this i'd read into the lines
""I spent the summer in a tent beyond Montauk at the extremity of Long Island. The Magical Retirement made it clear that the current was exhausted. I had finished my work in America and began to prepare my escape.""
to mean the "flow" of magick possibly exhausted, ie producing little to nothing substantial...?shrugs normally words inter-relate in such ways