James Anderson brought up his 950th first-class wicket for Lancashire during their game against Durham.
Nick Browne's century guided Essex into a position of dominance against Nottinghamshire as the 2017 champions continued to underline their title credentials.
The opener finished unbeaten on 163 with his side on 345 for three, giving them an advantage of 132 at the halfway stage of the contest against Division One's bottom side.
Browne has batted for seven and a half hours, sharing century stands with both Dan Lawrence and Ravi Bopara as Notts struggled to make inroads into the batting lineup.
Essex have won four of their last five matches, drawing the other, and have charged up the table to close the gap on leaders Somerset to just 13 points before this round of matches.
Jamie Overton's five-wicket haul gave Somerset a narrow advantage over third-placed Hampshire despite Sam Northeast's third century of the season.
Overton claimed five for 66 to leave Hampshire on 329 for eight at the close, trailing by 79 runs.
Earlier, Northeast hit a fine 101 off 175 balls, with 13 fours and a six, sharing stands of 101 with Ajinkya Rahane and 82 with Rilee Rossouw.
Mark Stoneman's first Championship century of the season helped Surrey claim a slender first-innings lead of 35 late in the second day against Yorkshire at Scarborough.
Stoneman's 100 off 167 balls - he was out two balls after reaching his milestone during the afternoon - was the feature innings as the champions, replying to 327, closed on 362 all out.
Bat continued to dominate ball at Canterbury as Warwickshire made a strong start in replying to Kent's mammoth first-innings total.
After seeing the hosts post a huge 585 for seven declared - courtesy of a Championship-best 166 from Daniel Bell-Drummond and Sean Dickson's season's-best 161 - the visitors countered with an unbroken opening stand worth 142 in the 47 overs through to stumps.
Division Two leaders Glamorgan enjoyed another productive day at Cardiff in their clash with Worcestershire.
Glamorgan extended their total to 449 before reducing their visitors to 191 for five - a lead of 258 with two days remaining.
Lancashire began this round of matches just a point behind Glamorgan having played a game fewer and they bowled their way into a strong position against Durham at Sedbergh School - the County Championship's newest venue.
The visitors closed on 199 for five, still trailing Lancashire's first-innings score by 138 runs, thanks to a two-wicket burst from James Anderson which brought up the England paceman's 950th first-class wicket.
Having resumed on 275 for five, Lancashire went on to post a first-innings total of 337 as captain Dane Vilas made 72.
In reply, Australian opener Cameron Bancroft made 77 but Durham slipped from 136 for one to 197 for five.
Northamptonshire are on course to claim their first County Championship win of the season after bowling out Sussex for their lowest total for 12 years.
Bottom of the second division going into the fixture, Northamptonshire ended day two at Hove with an overall lead of 379 on 212 for four in their second innings after Sussex had earlier been dismissed for 106.
Ben Sanderson finished with six for 37 before Northants chose not to enforce the follow-on.
Middlesex's difficult season continued as they face an uphill struggle to save their match at Derby after a dominant day for Derbyshire's batsmen.
Leus Du Plooy scored 118 and Anuj Dal 92 as the home side took their first innings to 557 for six before declaring.
The visitors slipped to 65 for two before Nick Gubbins and skipper Dawid Malan added 67 in 22 overs but Luis Reece removed Gubbins to leave Middlesex on 135 for three, 422 runs behind.