Maxwell's needle apparatus is used to determine the shear modulus (?) of the material of a wire of uniform cylindrical cross section. Conventionally, a single observation is taken for each observable, and the value of ? is calculated in a single shot. A modification to the above apparatus is made by varying one of the observables, namely the mass of the hollow cylinder (m[subscript h]). With this modification five sets of values of mass difference (m[subscript s] - m[subscript h]) are taken and corresponding values of difference of the squares of time periods (T[subscript 2][superscript 2] - T[subscript 1][superscript 2]) are plotted on the graph for calculating the value of ?.