Show to help rapid transit the blasting off of a 15 foot layer of rock from the top of reef in east river new york just east of the lower end of manhattan and at the same time the boring of two tunnels under this reef constitute a dual engineering undertaking now in progress that Is calling for unusual precautions and skillful procedure says popular mechanics magazine the tunnel will serve as a new rapid transit link between manhattan and brooklyn the cost of cutting down the reef Is being borne by the federal government and new york city at mean low tide the reef has been 25 feet below the surface a distance that Is not regarded as aa safe for some heavily laden boats the new depth of 40 feet will be more sufficient it Is believed the tunneling el which could not well be delayed until after the channel was deepened is progressing ahead of and faster than the river bottom excavating which Is proceeding at right angles to the tunnels |