  A simple asperity model using random process theory is developed in the
presence of adhesion. Using the DMT model for each individual asperity, and
asymptotic results at large separations, a new adhesion parameter is found, on
which the model depends, namely $\theta=\frac{w}{E^{\ast}\sqrt{m_{2}/\pi}
m_{0}^{1/2}}$, where $w,E^{\ast},m_{2},m_{0}$ are respectively surface energy,
combined elastic modulus, variance of slopes and of heigths of the asperities.
This parameter perhaps improves the previous parameter proposed by Fuller and
Tabor which assumed identical asperities. the effects of adhesion are found in
practice only for {\theta}>0.15. Some implications are discussed and
comparisons with recent results are attempted.
