Is it a coincidence that Bitcoin is at a high when the dollar is at a new low? That’s a question the solons on Capitol Hill might want to pose to the Federal Reserve chairman, Jerome Powell, when he deigns to pay a visit Wednesday and Thursday. While markets are likely to focus on the future course of interest rates, it would surely be nice to hear Mr. Powell’s explanation as to the state of the dollar, the value of which the Fed is tasked with protecting.