His "thermometer kirb," he himself says, "is composed of two thin plates of brass and steel, riveted together in several places, which, by the greater expansion of brass than steel by heat and contraction by cold, becomes convex on the brass side in hot weather and convex on the steel side in cold weather; whence, one end being fixed, the other end obtains a motion corresponding with the changes of heat and cold, and the two pins at the end, between which the balance spring passes, and which it alternately touches as the spring bends and unbends itself, will shorten or lengthen the spring, as the change of heat or cold would otherwise require to be done by hand in the manner used for regulating a common watch." Although the method has since been improved upon by Leroy, Arnold, and Earnshaw, it was the beginning of all that has since been done in the perfection of marine chronometers.

Indeed, it is amazing to think of the number of clever, skilful, and industrious men who have been engaged for many hundred years in the production of that exquisite fabric--so useful to everybody, whether scientific or otherwise, on land or sea the modern watch.
It is unnecessary here to mention in detail the particulars of Harrison's invention.

These were published by himself in his 'Principles of Mr.Harrison's Timekeeper.' It may, however, be mentioned that he invented a method by which the chronometer might be kept going without losing any portion of time.

This was during the process of winding up, which was done once in a day.

While the mainspring was being wound up, a secondary one preserved the motion of the wheels and kept the machine going.
After seven years' labour, during which Harrison encountered and overcame numerous difficulties, he at last completed his first marine chronometer.