Surrey 188 for 5 (Foakes 57) trail Somerset 344 (Bartlett 137) by 156 runs
A classy 57 by Ben Foakes stood out in testing batting conditions on a weather-affected second day at Guildford, in which Surrey reached 188 for 5 in reply to Somerset's 344.
Only 36.2 overs were bowled before bad light and rain cut short proceedings from shortly after 2pm until 5.30pm, when a further 18.4 overs were possible, but Foakes' half-century rallied Surrey from the depths of 38 for 3 in a fourth-wicket partnership worth 81 in 22 overs with Scott Borthwick.
Borthwick's two and a half hours of resistance eventually ended, after a 118-ball 36, in that tricky final session when he nicked a push-drive at a ball from Craig Overton. All-rounder Ryan Patel, however, contributed a punchy 40 not out from 69 balls, as sunshine warmed the early evening's play, while Will Jacks hung on to remain unbeaten on 13.
Foakes hit ten fours in a fine 70-ball effort, before edging the pacy Jamie Overton to keeper Steven Davies two overs before the players left the field 5.2 overs into the afternoon session. Overton had figures of 2 for 20 from 6.2 overs when the players left the field but Patel took three fours in an over off the fast bowler when play resumed - two thumping square cuts and a rasping extra cover drive - to spoil his figures somewhat.
The Overton twins and Jack Brooks had all earlier struck with the new ball in the day's opening hour, after Surrey had resumed their first innings on 0 for 0. Overcast conditions encouraged a five-pronged Somerset seam attack but Mark Stoneman started brightly, hitting three offside fours and a pick-up six off Craig Overton.
After reaching 21 from 22 balls, though, left-hander Stoneman played no stroke at a ball from Brooks which swung in wickedly late to pluck out his off stump.
Burns, who laboured for 39 balls to make just 2, then drove loosely at Craig Overton to give Marcus Trescothick a sharp catch at second slip and Dean Elgar soon joined his captain in the pavilion when he was out for 1 to Jamie Overton's first ball of the match.
Having replaced his brother in the attack, Overton swung a good length ball back into Elgar's pads and won the leg-before appeal. It was also his first ball in championship cricket this season for Somerset, although he took six wickets in the second division for Northamptonshire late last month during a short loan spell.
Foakes counter-attacked with some high-quality strokes, including one powerful pull for four off Jamie Overton and, later, there was another meaty pull to the boundary when Jack Leach's left-arm spin was introduced just before lunch.
Borthwick, by contrast, was more circumspect in the testing conditions but he did drive Tim Groenewald through extra cover for four with a flourish in the morning session.
On 23 when bad light and then rain intervened, he hit one more lovely cover driven four off Brooks before being dismissed, leaving Patel and Jacks to make sure Surrey did not lose another wicket before stumps. Craig Overton, who finished the day with figures of 15-8-26-2, was the pick of Somerset's bowlers.