The Knudsen cell mass spectrometric method has been employed to measure the partial pressures of the Si-7 and Si-8 clusters under equilibrium conditions above liquid silicon, contained in a boron nitride liner inside a graphite Knudsen cell. Gaussian 2 (G2) theory and B3LYP density functional method were employed to determine the geometry, the vibrational frequencies, and the binding energy of the Si-8 cluster. From the all-gas analyzed equilibria the following atomization enthalpies, Delta H-a(0)o(Si-n), and enthalpies of formation, Delta (f) H-298.15(o)(Si-n), in kJ mol(-1), have been obtained: Si-7, 2381 +/- 36 and 743 +/- 36; Si-8, 2735 +/- 65 and 837 +/- 65. Expeiimental literature values for the electron affinities of Si-n(n = 3 - 8) have been combined with present and previous results to obtain the bonding energies for the Si-n(-) (n = 3 -8) cluster anions. The experimental atomization energies are compared with available theoretical values.