There was also useful batting practice for JP Duminy (53), Morne Morkel (38), Robin Petersen (33 not out) and AB de Villiers (23) on a day dominated by news of Mark Boucher's retirement from international cricket.
Somerset had added 50 for one to their first innings score of 312 for eight declared by the end as the game, which will always be remembered for Boucher's horrific eye injury on Monday, drifted to an inevitable draw.
After the start of day two had been delayed an hour by rain, Jacques Kallis retired not out on his overnight score of 45. From 96 for two at the start, the tourists progressed sedately to 134 before de Villers, who had replaced Kallis, was bowled off a thin inside edge by medium-pacer Peter Trego for 23, having faced 39 balls and hit 5 fours.
Amla dropped anchor and reached a solid half-century off 105 balls, with 5 fours, taking more than an hour to add 16 to his overnight score of 34.
Duminy briefly livened up proceedings, smashing a big six over mid-wicket off 21-year-old left-arm spinner Jack Leach, making his Somerset debut, but after all the first day drama it was almost as if the South Africans had set their stall out for a quiet morning. Amla had made 64 when bowled by Leach with what proved the last ball before lunch to make it 187-4.
The afternoon session will be long remembered by Somerset's teenaged seamer Craig Overton, who was on a hat-trick when he bowled Vernon Philander for six and then had Dale Steyn caught behind by replacement wicketkeeper James Regan, an Academy player.
Peterson survived the next delivery, but in his next over Overton had Duminy lbw playing down the wrong line and the England Under-19 player had then taken three wickets for one run in the space of seven balls. Duminy hit 4 fours and 3 sixes in facing 100 balls.
On his departure, Morkel produced some extravagant blows, striking 5 fours and a six before being caught at deep square by Craig Overton off the bowling of twin brother Jamie. With Kallis electing not to continue his innings, the South Africans declared when Imran Tahir fell leg before to Dockrell for a duck, Petersen ending unbeaten on 33 off 60 balls.
When Somerset batted again Arul Suppiah bagged a pair, pinned leg before by Philander, whose new ball partnership with Steyn again looked impressive. Alex Barrow was unbeaten on 31 when the teams shook hands at just before 5pm.