Measurements of the effective field penetration depth λ, breakdown field, Hb, supercooling field, Hsc, and superheating field, Hsh, are used to investigate the superconducting properties of silver caused by the proximity of niobium in the temperature range 5 mKb data yields the coherence length ξN=α/T with α=1.46 µm K. This value is in very good agreement with the theoretical value \hbarvF/2πk=1.70 µm K.