Partick eased to a comfortable William Hill Scottish Cup victory over Highland League side Formartine United with a 4-0 win at Firhill.The tie was as good as over mid-way into the first-half as a Chris Erskine brace and a Steven Lawless strike gave the home side a well-earned 3-0 lead.Abdul Osman's second-half finish added gloss to the performance in a match where the visiting Highlanders failed to test Jags keeper Tomas Cerny.The home side took the lead on 10 minutes when Erskine rolled the ball into the net following a neat-cut back from David Amoo on the byline.Erskine should have had his second shortly after, scuffing the ball wide when through on goal after a neat interchange with Kris Doolan.The Jags did net a deserved second goal on 29 minutes when Lawless arrowed home a low drive following patient build-up play in the midfield.And seconds later, a fine solo run and finish from Erskine effectively sealed the victory for Thistle after the forward was played through by strike-partner Doolan on 30 minutes.Early in the second half, Erskine struck a ferocious half-volley past the near post as the front-man chased his hat-trick.Thistle added a fourth goal on 64 minutes when the impressive Lawless chipped a ball into the box for Osman to convert with a first-time finish.The Jags controlled the remaining half hour of the game, however Scott Barbour should have netted a consolation for Formartine as he flashed a shot with the goal at his mercy.In the dying moments of the game, Amoo was nearly rewarded for his strong display as he struck a low drive inches wide of goal, before the returning Mustapha Dumbuya fired a shot narrowly over the bar after an enterprising run.ends