Harry of Ciro's South Side is a mint-and-lemon gin drink strained into a tumbler and lengthened with syphon.
Harry of Ciro's ABC of Mixing Cocktails by Harry of Ciro's (1923, p.80) — Harry of Ciro's 1923
| 1 glass | gin — Gin (Gordon) | base |
| 1 lemon | lemon juice — Lemon Juice | base |
| Soda water — Syphon | dilution | |
| mint — Fresh Mint | other | |
| 1 teaspoonful | sugar | sweetener |
This matters because it preserves a lengthened South Side branch rather than only the shorter cocktail-glass form.
The syphon finish moves this toward the Collins/highball side of service.
L'Art du Shaker by Dominique Migliorero (1925, p.63)
| 0.5 lemon | lemon juice — Lemon juice | acid |
| crushed ice — Crushed ice | base | |
| 1 liqueur glass | gin — Gin | base |
| mint — Fresh mint leaves | other | |
| 1 coffee spoon | powdered sugar — Powdered sugar | sweetener |
Garnish: Mint
Ice: Crushed ice
Barflies and Cocktails by Harry McElhone and Wynn (1927, p.76) — Syphon finish
| 1 glass | gin — Gin (Gordon) | base |
| 1 lemon | lemon juice — Juice of 1 Lemon | base |
| Soda water — Syphon | dilution | |
| mint — Fresh Mint | other | |
| 1 teaspoonful | sugar | sweetener |
This matters because it preserves the South Side in a lengthened tumbler form rather than a shorter later-classic template alone.
See also: Tom Collins, Gin Daisy