Define Calorie what is the relation between calorie and mechanical equivalent of heat?

Calorie: The quantity of heat required to rise the temperature of 1 gm of water through 1°C at a pressure of 1 atm is called calorie.
W = JH
$\Rightarrow \frac{\text{ Mechanical work }}{\text{ Heat energy }}=\mathrm{J}=\frac{4.2\text{ Joule }}{\text{ Calorie }}$
Where J is called mechanical equivalent of heat