Leaders Surrey boosted their Division One title ambitions by taking a grip on their contest with Durham at Chester-le-Street.
Surrey, resuming on 182-5 after bowling Durham out for 153 on the opening day, made 322 with Dan Lawrence (88) and Jordan Clark (82) leading the way.
Durham reached 222-5 at the close - a lead of 53 - with firm resistance from Emilio Gay (99), who fell one short of a century.
Colin Ackermann went for 43 just before the close as Sai Kishore's (2-36) two wickets gave Surrey hope of a fourth victory of the season.
Second-placed Nottinghamshire's hopes of staying in touch with the leaders were boosted by skipper Haseeb Hameed's (103no) unbeaten century at Trent Bridge.
Responding to Somerset's 438 all out, Hameed made his third hundred of the season from 179 balls, taking him past the 1,000-run mark this summer.
Freddie McCann chipped in with 48 and Joe Clarke was undefeated on 26 as Nottinghamshire closed on 189-2.
Essex made a massive 602-6 against Warwickshire with bowlers short of joy on a batting-friendly pitch at Chelmsford.
Centuries from Charlie Allison (133) and Michael Pepper (107no) added to Tom Westley's 148.
Warwickshire also made hay with the bat to close on 140-2 as skipper Alex Davies made 58, with Dan Mousley unbeaten on 54.
Yorkshire established a first-innings lead over Sussex at Scarborough after bowling out the visitors for 222.
Jack White was the pick of the bowlers with 3-25 from 19 overs as the wickets were shared around.
Adam Lyth (115 off 233) and James Wharton (85 off 130) shared a 168-run partnership for the third wicket, and Yorkshire will resume play on day three 292-4 - a lead of 70.
Worcestershire are 106 runs adrift of Hampshire at the halfway stage with eight first-innings wickets left at New Road.
The visitors were dismissed for 293 after Tom Prest's 54 and it looked an unsatisfactory score after the hosts reached 187-2
Jake Libby (70no) and Adam Hose (82no) were defiant with an unbroken third-wicket partnership of 126.
In Division Two, James Anderson (2-20) celebrated his 43rd birthday with two Glamorgan second-innings wickets, but the Welsh county are on top against Lancashire at Emirates Old Trafford.
Glamorgan dismissed the hosts for 137 as leg spinner Mason Crane recorded career-best figures of 6-19 and the Red Rose county lost their last eight wickets for 64.
Anderson gave Lancashire hope by bowling Zain ul Hassan (12) and claiming a catch off his own delivery to dismiss Asa Tribe (11).
But Kiran Carlson (43no) and skipper Sam Northeast (26no) steadied the ship and Glamorgan lead by 219.
Leaders Leicestershire reached 471 against Kent thanks to an incredible last-wicket stand of 108 between Tom Scriven (99) and Josh Hull (35no).
Scriven made a career-best 99 as the Foxes secured maximum batting bonus points at Canterbury.
Matt Parkinson took 7-137 to record his best first-class for Kent, and the hosts closed on 203-3 as Ben Compton made an unbeaten 101.
New Zealand batter Kane Williamson scored 153 to steer Middlesex to 445 at Cheltenham, with Gloucestershire 54-1 in reply.
Martin Andersson was Derbyshire's mainstay with 105 in their 377 against Northamptonshire.
After slipping to 154-5, George Bartlett (60no) and Justin Broad (64no) coaxed Northamptonshire to 265-5, 112 adrift.
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