He and Willie McOustra were signed by the club after playing in a friendly against The Kaffirs, a touring team from the Orange Free State.

[3] He made his debut for Thistle in November, replacing Willie Paul in the forward line in a 2–0 win over Airdrieonians, and scored his first goals later in the month, against Morton.

At the end of the season, Blackwood was recalled by Celtic, who then sold him to Football League Second Division club Woolwich Arsenal.

[7] After joining Woolwich Arsenal in May 1900, Blackwood scored on his debut, in a 2–1 win over Gainsborough Trinity on the opening day of the 1900–01 season.

[5] Taking over centre forward duties from Billy Bridgeman, he scored on his debut, against Portsmouth on 26 December, but his four-match run in the team coincided with one of the club's worst ever losing streaks.