THE SECOND LONGITUDE TIME - KEEPER

Harrison's No.2

On 30 June 1737 Harrison proposed to a Board of Longitude meeting that a second and improved longitude time-keeper should be constructed, viz. H.2. This was approved. Harrison then sought 500 pounds from the Board to help meet the costs of developing and constructing H.2. This the Board also approved although it imposed harsh conditions stipulating that this and all future longitude time-keepers should be surrendered to the State (Quill, 1966:48).

In 1739 H.2 was completed. Taller and heavier than H.1, H.2 was less deep so took up less deck space - an important consideration at the time. The main innovation in the mechanism of H.2, one which Harrison used in all his subsequent longitude time-keepers was a remontoire. Remontoire mechanism ensures that the force on the escapement is constant; this improves the accuracy of the clock. It was the use of the remontoire that Quill (1966:59) believes "was largely responsible for [Harrison’s] eventual success."

The actual performance of H.2 is not known because it was never trialled at sea, partly from fear of capture by the Spanish.

H.2 was the last time- keeper that James Harrison was to work on, the partnership having broken up with his brother some time in 1739. The reasons for the break-up are not clear although Quill (1966:61) speculates that it may have been due to some degree of ‘personal friction’ between the brothers. Following the break-up James appears to have withdrawn completely from the pursuit for longitude leaving John to continue the quest alone.