29 JANUARY 1977, Page 25

Kelvin

Sir: Mr Wheatcroft is slightly incorrect in saying that the Kelvin is a new temperature scale (15 January). It has been used by

scientists for a number of years now as the universally accepted SI unit of thermodynamic temperature.

However, I do sympathise with him should Germany adopt the scale. The task of subtracting 270 (accurately 273.16) then doubling and adding thirty to obtain the Fahrenheit equivalent is unenviable, and yet although there seems to be little difference between 283K (note that there is no ° sign) and 297K, the former is distinctly chilly (50"F) and the latter rather warm (75 'F),

Anne Blonstein Selwyn College, Cambridge