It answered even better than the first, and though it was not tried at sea its motions were sufficiently exact for finding the longitude within the nearest limits proposed by Act of Parliament.
Not satisfied with his two machines, Harrison proceeded to make a third.

This was of an improved construction, and occupied still less space, the whole of the machine and its apparatus standing upon an area of only four square feet.

It was in such forwardness in January, 1741, that it was exhibited before the Royal Society, and twelve of the most prominent members signed a certificate of "its great and excellent use, as well for determining the longitude at sea as for correcting the charts of the coasts." The testimonial concluded: "We do recommend Mr.Harrison to the favour of the Commissioners appointed by Act of Parliament as a person highly deserving of such further encouragement and assistance as they shall judge proper and sufficient to finish his third machine." The Commissioners granted him a further sum of 500L.
Harrison was already reduced to necessitous circumstances by his continuous application to the improvement of the timekeepers.

He had also got into debt, and required further assistance to enable him to proceed with their construction; but the Commissioners would only help him by driblets.
Although Harrison had promised that the third machine would be ready for trial on August 1, 1743, it was not finished for some years later.
In June, 1746, we find him again appearing before the Board, asking for further assistance.

While proceeding with his work he found it necessary to add a new spring, "having spent much time and thought in tempering them." Another 500L.