How does Gorgias see rhetoric as a bridge between art and science?

Rhetoric is referred to as an art itself in the conversation. Rhetoric can function as persuasion and a means of delivering information, just as arts and sciences (such as math, using the language of numbers) do. Rhetoric is "language" and since all arts and sciences use some form of language, their success is based on the comprehensiveness of their language, which would be rhetoric.