38 POPULAR LECTURES AND ADDRESSES. 



last century. Harrison died in Red Lion Square, 

 London, in I/76." 1 



Harrison's compensation curb, here referred to, 

 was a contrivance in which the bending of a com- 

 pound bar of brass and steel soldered together was 

 applied to shorten the vibrating portion of the 

 hair-spring of the watch when the temperature 

 rises, and elongate it again when the temperature 

 falls. The very different method of compensation 

 subsequently invented by Earnshaw was no doubt 

 much superior, but Harrison's curb must always be 

 interesting as the first successful method for com- 

 pensating the temperature error of a watch, and 

 the first usefully applied to determine the longitude 

 at sea. 



29. The most important improvement in marine 

 chronometry since the time of Earnshaw has been 

 made by Mr. Hartnup, Astronomer to the Marine 

 Committee of the Mersey Docks and Harbour 

 Board of Liverpool. It had been long known that 

 the simple compensation balance, whether of 

 Harrison or Earnshaw, however perfectly executed 



1 Chambcrs's Encyclopaedia, Art. "Harrison." 



