Gentle, J.

1. The plaintiff, the Corporation of Madras, was the owner of 21 steam rollers which were used in connection with the discharge of the duty of making, repairing and maintaining roads within the city. Acting through the Commissioner of Police, the defendant (hereinafter called "the local Government") required the plaintiff to pay the sum of Rs. 16,170 as the amount of tax alleged to be leviable upon these steam rollers under the provisions of the Madras Motor Vehicles Taxation Act, 1931 (hereinafter called "the local Act") for the period from 1st April, 1931 to 30th April, 1934. The plaintiff contended that these rollers were not motor vehicles within the meaning of the local Act and that no tax was leviable upon them. Correspondence took place between the plaintiff and the local Government eventuating in 1936 by a letter addressed to the Corporation informing it that if payment of the sum of Rs. 16,170 was not made, the local Government would adjust this sum by an equivalent deduction from the grant payable to the plaintiff during that year. Thereupon, on 30th March, 1936, the plaintiff paid the above sum under protest, see Exs. P-1 and P-2. On 14th August, 1936,