John Harrison Sea Clocks

John Harrison Sea Clocks

Our range of Sea Clocks are inspired by the great John Harrison. In each clock we have embodied at least three of the basic principles from Harrison's first Sea Clocks.

Perhaps his most well known invention is the unique escapement, which gives the clock its popular name, 'The Grasshopper'.

The subtle and almost silent 'lock and release' action of the pallets permits them to work without oil (and consequently be free of the effects of changes in viscosity) and at the same time make it so enduringly fascinating to watch.

The Astronomer Royal, Edmund Halley (c1656-1742) was a proponent of the Lunar distance method for determining longitude. The observations and calculations required for this method took many hours and were prone to error. The hand painted Moonphase dial (each signed and numbered by the artist) on the Moonphase model symbolises this alternative method.

The Moonphase Sea Clock (shown left)
Probably the most popular clock in our range of Sea clocks, the Moonphase Sea clock embodies 3 of John Harrison's basic principles used his original H1. It also provides in the Moonphase dial a representation of the competition (Lunar distance method) he faced for the solution to the Longitude problem back in the 18th Century.

The compound pendulums and Grasshopper escapement are positioned at the front of the clock making the subtle and almost silent "lock & release" of the pallets enduringly fascinating to watch.

Almost every piece is made in the workshops of Sinclair Harding using a combination of modern technology, materials and traditional finishing techniques. Every care is taken at each stage in the making and build to ensure that the final clock performs to a standard, which justifies the association with John Harrison.

All the brass parts are Gold or Rhodium plated and the steel parts made from a high grade stainless steel. The Standard base is made from an English Walnut frame, with a highly figured Burr veneer top, other options are Mahogany or Rosewood.

HEIGHT: 45cm. WIDTH: 32cm. DEPTH: 21cm.

“Each clock is individually serial numbered and so confident are we of our quality that each clock comes with a guarantee for the lifetime of the original owner.”


    Standard Sea Clock

    Standard His & Hers Sea Clock

    Two styles of clock are available they are named “His” and “Hers”. As with all Sinclair Harding clocks a selection of finish and base materials can be specified to make your clock a very personal piece.

    Each clock is individually serial numbered and is protected by a framed glass shade – not shown.

    Sea Clock on a walnut base with glass shade

    Sea Clock Bases & Shades

    The clocks are normally mounted on a base of selected figured mahogany or walnut, inlaid with Brass on to which the winding key and hand setter are attached. The base is French polished which is generally recognised as the finest finish that can be applied to wood.

    The clocks are protected by a framed glass shade into which holes are provided in the glass allowing the winding to be carried out without having to remove the shade.

    The Perfect Team


    The engraved dials are hand silvered as they were in Harrison's day. The unusual seconds hand deserves a special study. It sweeps through 240 degrees going from 0-60 seconds before vanishing, only to reappear instantly at zero again.

    The Perfect Team

    The 8 Day Movment

    The 8 day movement is protected by a framed glass shade, which incorporates a winding hole to avoid having to remove the glass each week, or a glass shade with an opening door can be provided if desired.

    All parts of each clock are hand finished (even the ones you cannot see!) and all the solid Brass parts are protected with a thin layer of Gold or Rhodium.

    The Fusee Chain

    The Fusee

    Driven by a handmade chain some 60 “ (152 cm) long. The curved click spring is made from stainless steel, wire eroded, followed by hammering to impart the spring properties.

    Moonphase Sea Clock Rear View

    The Invar Pendulums

    The Invar pendulums are linked at the back, which allow the clock to function 'out of level'. Their gentle action gives each clock that restful quality which is so typical of an earlier more tranquil age.

    Moonphase Sea Clock Rear View

    Glass Base

    All John Harrison Sea Clocks have the option to be mounted on a contemporary glass base.

    Moonphase Sea Clock Rear View

    Rear View


    Where to find our clocks »

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      Our clocks can be seen in exclusive outlets throughout the world.

      Please visit our Retailers page for a complete list.

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