The second spectrum of silicon

New observations of the spectrum SiII from $\lambda$ 700 to $\lambda$ 9500 are described, 300 lines being listed in addition to those previously assigned to this spectrum. The analysis includes details of the perturbations of the 3s$^2$nx$^2$X series up to x=g. Structures of type 3s3p($^3$P)nx up to x=f have been identified and many peculiarities found. A large proportion of the levels show auto-ionization effects, even up to a term at 25000 cm$^{-1}$ above ionization. The same term also shows an anomalous degree of excitation in the hollow cathode for two levels which cannot auto-ionize.