The peculiar properties of a train of three linear polarizers, theoretically treated by R. C. Jones, are experimentally investigated. A combination of three sheet polarizers and a wave plate of adequate relative retardation is used to examine the birefringence of the polarizer. Estimated value of relative retardation of the polarizer (Polaroid Corp. product, H type, t=0.3 mm) is 0.24 λ for a monochromatic light of 440 mμ. Calculated and observed values of the change in the shape of transmittance curve by the principal axes being out of alignment are in fair agreement. Adjustment of the alignment was possible down to 1/2° which was sufficient for the required accuracy.