Scale 1:48. Drawing showing the sheer lines with inboard detail, framing and trusses, the body plan, the longitudinal half breadth and details of iron trusses and breast hooks for four wooden three-masted paddle steamers of the same class for Cunard (The British & North American Royal Mail Steam Packet Company, Glasgow). These were Britannia (1840), built by Robert Duncan, Greenock; Acadia (1840), built by John Wood & Co, Port Glasgow; Caledonia (1840), built by Charles Wood, Dumbarton; and Columbia (1840), built by Robert Steele & Co, Greenock.

The plan includes the Admiralty Letter Book Numbers S4197 and S11280/56, indicating that these were drawn for, and sent to, the Admiralty. William Blessley was a draughtsman at Portsmouth Dockyard in 1836.

Inscriptions:
- "A drawing of the Halifax Steam vessels of N 240 HP"
- In pencil: "Mr Cunard
Britannia }
Acadia } as this drawing"
Caledonia }
Columbia }