Leaders Derbyshire bowled out Essex for 245 but crashed to 28 for three in reply in their LV= County Championship Division Two clash at Derby.
Left-arm spinner David Wainwright took four for 64 as Graham Napier top-scored for Essex with 42 and added 74 for the eighth wicket with David Masters.
The latter then took two for three in seven overs against his former county and Napier removed nightwatchman Tony Palladino before the close.
Bad news before the toss was soon swept aside by Yorkshire on the first day of their important match against Gloucestershire at Scarborough.
The visitors were dispatched for 215 after being nine for four at one stage, with three wickets apiece for Steven Patterson, Moin Ashraf and Azeem Rafiq, but Yorkshire then suffered one or two upsets of their own before finishing the day well placed on 61 for two.
Yorkshire, holding third spot, need a win to boost their promotion chances but they were unable to include senior paceman Ryan Sidebottom because of back spasms or Richard Pyrah, who on Monday broke a bone in his left hand for the second time this season.
Brendon Nash made 108no as Kent closed on 322 for six against Leicestershire at Grace Road.
The West Indian added 134 with Geraint Jones, who was dismissed for 52 from the last ball of the day. Openers Rob Key (68) and Sam Northeast (52) earlier put on 110 while Robert Taylor took four for 77.
Opener Niall O'Brien's unbeaten century led Northamptonshire to 241 for four against Glamorgan in Cardiff.
The Ireland wicketkeeper batted throughout the first day to reach 114 from 298 balls and put on 154 with Alex Wakely (75).