Emission spectra of Indium have been photographed over the spectral range from 340A° (177A° in 2nd order) to 9500A° using the disruptive electrodeless and spark in helium sources. About 4000 lines of Indium have been measured and 36% of these lines are classified as belonging to the spectra of InI,InII, Inlll, InlV and InV. The analyses of Inlll and InlV have been revised and extended to include 4d¹ºns(n=5 to 12), `4d¹ºns(n=5 to 9), 4d¹ºnd (n=5 to 9) and 4d¹ºnf(n=4 to 7). Polarisation theory has been applied to 4d¹ºng(n=5 to 9) and 4d¹ºnh (n=6 to 9) series and the ionization potential deduced from this is reported to be 226191.3 cm⁻¹. The dipole polarizability of the 4d¹º core is estimated to be 3.48a₀³ . Most of the expected terms of 4d⁹ 5s5p and 4d⁹ 5s6s are established for the first time. Some of the levels of 4d⁹ 5s5d are also added as well as some levels from the higher configurations 4d⁹ 5s7s and 4d⁹ 5s6d. In triply ionised Indium the new additions are to the 4d⁹5d, 4d⁹ 6d, 4d⁸5s and 4d⁹6p configurations. Houston's theory of intermediate coupling has been successfully applied to 4d⁹ns (n=5,6 and 7) terms. Tentative values are given to several levels of 4d⁸5s5p and 4d⁹4f terms. The double limit of InlV is calculated from 4d⁹ns series as 461875 cm⁻¹ and 468989 cm⁻¹. Experimental results are compared with the theoretical calculations for some of the configurations of Inlll and InlV. / Science, Faculty of / Physics and Astronomy, Department of / Graduate