Bowling from the Somerset Pavilion End, Ball had Marcus Trescothick caught behind driving for 25 and Tom Abell snapped up at mid-wicket for eight.
From 33 for two, having won the toss, the home side rallied thanks to an unbroken third-wicket stand of 66 between skipper Chris Rogers (39 not out) and James Hildreth (25 not out).
Hildreth had to bat with a runner having been struck a painful blow on a foot by a delivery from Ball.
There were signs of turn from both ends and Somerset could feel well satisfied with a lunch position of 99 for two from 33 overs. Ball’s figures were two for 16 from nine overs.