Planning for six metal-hulled corvettes began in 1876.
 These vessels, which became the Comus-class corvettes, were designed by Nathaniel Barnaby.
Among the Royal Navy’s last sailing corvettes, they supplemented an extensive sail rig with powerful engines.
 Unlike their French rivals, which built fast steamers and needed neither long range nor a full rig of sail, the Royal Navy required their cruisers to be capable of long voyages away from coaling stations.
 Their ships therefore had a beamy hull to handle their sails, making them slower under steam than their French counterparts.

The British vessels were similar in appearance and layout to the older wooden and composite-hulled small cruisers they were intended to replace, albeit larger and more powerfully armed.
The vessels were among the first of the smaller cruisers to be given metal hulls, with frames of iron or steel.
 The forefoot was a ram forged from brass, a feature then in vogue.
In common with older wooden vessels, their hulls had copper sheathing over timber beneath the waterline, but that timber simply served to separate the iron hull from the copper sheathing so as to prevent electrolytic corrosion.
 The timber extended to the upper deck; it was in two layers from the keel to 3 ft (.9 m) above the water line, and one layer above.

In an early case of a single builder taking responsibility for building an entire class, contracts for these first six vessels were all awarded to the John Elder & Company at Govan on the Clyde.
They were all fitted with 3-cylinder compound engines, with one high-pressure cylinder of 46 inches diameter being flanked by two low-pressure cylinders of 64 inches diameter.

Two to three years later, the Admiralty ordered an additional three vessels to be built to the same design.
Construction of these was awarded to the Royal Dockyards at Chatham and Portsmouth.
This second group differed by carrying a barque rig instead of the ship rig of the first six ships.
 The compound engines in the new batch were of 4-cylinder type, with two high-pressure cylinders of 36 inches diameter and two low-pressure cylinders of 64 inches diameter.

In the Comus class, the bow above the waterline was nearly straight, in contrast to that of wooden sailing ships.
 The corvettes had stern galleries, similar to older frigates, but the ports were false, and there were no quarter galleries.
 Boats were carried both amidships and at the stern.
 The ships flew a barque or ship rig of sail on three masts, including studding sails on fore and mainmasts.
The masts were stayed by shrouds which were anchored to chainplates affixed to the inside of the gunwales, rather than the exterior as in wooden sailing ships.
 Their sailing rigs enabled them to serve in areas where coaling stations were rare, and to rely on their sails for propulsion.

The vessels had two complete decks, upper and lower, with partial decks at the forecastle and poop.
 The forecastle was used for the heads and working space for the cables.
 The poop deck contained cabins for the captain, first lieutenant, and navigating officer, with the double wheel sheltered under its forward end.
 Between these was the open quarterdeck on which the battery was located.
 Under the lower deck were spaces for water, provisions, coal, and magazines for shell and powder.
 Amidships were the engine and boiler rooms.
 These were covered by an armoured deck, 1.5 inches (38 mm) thick and approximately 100 ft (30 m) long.
This armour was about 3 ft (90 cm) below the lower deck, and the space between could be used for additional coal bunkerage.
The machinery spaces were flanked by coal bunkers, affording the machinery and magazines some protection from the sides.
 The lower deck was used for berthing of the ship's company; officers aft, warrant and petty officers forward, and ratings amidships, as was traditional.
 The tops of the coal bunkers, which projected above deck level, were used for seating at the mess tables.
 The living spaces were well-ventilated and an improvement over prior vessels.

There were some refinements
Planning for six metal-hulled corvettes began in 1876.  These vessels, which became the Comus-class corvettes, were designed by Nathaniel Barnaby. Among the Royal Navy’s last sailing corvettes, they supplemented an extensive sail rig with powerful engines.  Unlike their French rivals, which built fast steamers and needed neither long range nor a full rig of sail, the Royal Navy required their cruisers to be capable of long voyages away from coaling stations.  Their ships therefore had a beamy hull to handle their sails, making them slower under steam than their French counterparts.
The British vessels were similar in appearance and layout to the older wooden and composite-hulled small cruisers they were intended to replace, albeit larger and more powerfully armed. The vessels were among the first of the smaller cruisers to be given metal hulls, with frames of iron or steel.  The forefoot was a ram forged from brass, a feature then in vogue. In common with older wooden vessels, their hulls had copper sheathing over timber beneath the waterline, but that timber simply served to separate the iron hull from the copper sheathing so as to prevent electrolytic corrosion.  The timber extended to the upper deck; it was in two layers from the keel to 3 ft (.9 m) above the water line, and one layer above.
In an early case of a single builder taking responsibility for building an entire class, contracts for these first six vessels were all awarded to the John Elder & Company at Govan on the Clyde. They were all fitted with 3-cylinder compound engines, with one high-pressure cylinder of 46 inches diameter being flanked by two low-pressure cylinders of 64 inches diameter.
Two to three years later, the Admiralty ordered an additional three vessels to be built to the same design. Construction of these was awarded to the Royal Dockyards at Chatham and Portsmouth. This second group differed by carrying a barque rig instead of the ship rig of the first six ships.  The compound engines in the new batch were of 4-cylinder type, with two high-pressure cylinders of 36 inches diameter and two low-pressure cylinders of 64 inches diameter.
In the Comus class, the bow above the waterline was nearly straight, in contrast to that of wooden sailing ships.  The corvettes had stern galleries, similar to older frigates, but the ports were false, and there were no quarter galleries.  Boats were carried both amidships and at the stern.  The ships flew a barque or ship rig of sail on three masts, including studding sails on fore and mainmasts. The masts were stayed by shrouds which were anchored to chainplates affixed to the inside of the gunwales, rather than the exterior as in wooden sailing ships.  Their sailing rigs enabled them to serve in areas where coaling stations were rare, and to rely on their sails for propulsion.
The vessels had two complete decks, upper and lower, with partial decks at the forecastle and poop.  The forecastle was used for the heads and working space for the cables.  The poop deck contained cabins for the captain, first lieutenant, and navigating officer, with the double wheel sheltered under its forward end.  Between these was the open quarterdeck on which the battery was located.  Under the lower deck were spaces for water, provisions, coal, and magazines for shell and powder.  Amidships were the engine and boiler rooms.  These were covered by an armoured deck, 1.5 inches (38 mm) thick and approximately 100 ft (30 m) long. This armour was about 3 ft (90 cm) below the lower deck, and the space between could be used for additional coal bunkerage. The machinery spaces were flanked by coal bunkers, affording the machinery and magazines some protection from the sides.  The lower deck was used for berthing of the ship's company; officers aft, warrant and petty officers forward, and ratings amidships, as was traditional.  The tops of the coal bunkers, which projected above deck level, were used for seating at the mess tables.  The living spaces were well-ventilated and an improvement over prior vessels.
There were some refinements 
Comus-class corvette