The tourists returned to the Grange on Saturday morning for the second day of their four-day match to resume on 335 for six, with Siddle eyeing his ton.
The right-arm paceman's previous best was the 87 he registered for domestic side Victoria against Western Australia in a Sheffield Shield match last September but he bettered that with an unbeaten 103 as his side declared on 372 for eight.
He was just 15 short of his target when play began under bright sunshine in the capital but the 28-year-old nearly slipped up when he was dropped on 93 by Calum MacLeod. He soon finished off his hundred with a boundary before visiting skipper Brad Haddin decided that was enough and called his batsmen in.
Siddle told Press Association Sport: "Yesterday it was a good opportunity to get out there and have a bit of a hit and see how it went. Today, well it was just good to get it out of the way. It was nerve-wracking but I got there in the end."
Scotland were without captain Kyle Coetzer and two other first-choice picks due to commitments with their English counties. And their absence showed as they could muster just 149 all out as they lasted a mere 44 overs.
For most of their first innings, it looked like they would struggle even to reach three figures as James Pattinson ripped through the middle order with three wickets at a cost of just 16 runs. Freddie Coleman was run out by Nathan Lyon for two after Matt Machan went for a needless single and that sparked a collapse that left the Scots worryingly shy on 83 for nine.
But Australia took their foot off the gas and allowed tail-enders Ian Wardlaw (33) and MacLeod (51) to step in and hammer a respectable look on to the Scots' scorecard with a series of flamboyant shots. Even with their 66-run last-wicket partnership, it still left the hosts 223 runs behind.
Siddle will be joined in the Ashes squad by Steven Smith, Lyon and full-team vice-captain Haddin and with the five-match series against the English in mind, the Australians opted against enforcing the follow-on and took the opportunity for some extra batting practice.
Jordan Silk (22) Usman Khawaja (eight) fell early, though, while Alex Doolan missed out on his half century as he was trapped LBW by Calvin Burnett on 47. Smith (18) went the same way to Iqbal as the Australians ended on 164 for four, putting them a massive 387 runs to the good.
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