Watch highlights of day two
Nick Compton's batting at Headingley placed new LV= County Championship winners Yorkshire in danger of a first home defeat of the season in the final round of matches.
He forged out a chanceless 156, by far his highest score of the summer, as Somerset replied to Yorkshire's modest first-innings score of 253 before closing the second day on 319 for three with a lead of 66.
Compton's previous-best score of the campaign was exactly 100 against Durham and his composure at the crease was such that it left one wondering why he has not achieved much more.
With the title already in the bag, Yorkshire's bowling was not as highly charged as usual but it was still good enough keep Compton and the other batsmen on their toes for much of the day as they made a determined attempt to help Somerset sign off on a winning note.
Yorkshire resumed on 241 for nine and they just managed to sneak a second batting bonus point before Jack Brooks was picked up at second slip by Marcus Trescothick off Peter Trego, who finished with 4-69.
Jack Leaning, the latest in the line of Yorkshire's young batting discoveries, remained unbeaten on 57 from 128 deliveries with eight boundaries, several of them struck sweetly through the off side.
Yorkshire know from long experience the destructive powers of Trescothick if he is allowed to settle in and three consecutive boundaries off Brooks helped in that process which was further aided when Joe Root dropped a low chance at third slip when the opener was on 28.
Steven Patterson, as economical as ever, broke the stand at 42 by having Johann Myburgh taken at second slip by Adam Lyth, and shortly afterwards he had an lbw shout rejected against Trescothick who moved to his half-century from 95 balls with nine boundaries.
Compton did not stay in the shadows, often outscoring his captain with firmly-middled shots and his fifty used up only 64 deliveries and contained nine fours.
Trescothick completed 1,000 championship runs for the season upon reaching 61 but Root, captaining Yorkshire in place of the suspended Andrew Gale, brought himself on to replace Adil Rashid.
His third ball was cut by Trescothick, on 66, but only into the safe hands of Lyth at slip, Root taking his bow at the end of the over.
In the evening session, Compton cut and steered Richard Pyrah for consecutive boundaries to reach three figures off 146 balls with 17 fours.
Together with Tom Abell, he took full advantage of flagging bowling, with the youngster going to his 50 from 86 balls, and Compton arriving at 150 from 224 deliveries with 23 fours and a six.
Patterson was thrown the new ball at 298 for two after 83 overs and it soon produced the desired effect as he breached Compton's defences to close the stand on 154 in 43 overs, Abell remaining unbeaten at the close on 66.