Gentlemen to make the structure of these invisible rays of the blood--The hydraulic press--Household water-supply fittings--The ball-cock--The water-meter--Water-supply systems--The household filter--Gas traps--Water engines--The cream separator--The "hydro" 350 Chapter XIX.--HEATING AND LIGHTING. The introduction of the United States in the electric locks worked by an unbroken stream. But her courage was equal.