Section 24 of the Income tax Act, 1922, in the relevant year of assessment read as follows : "(1) Where any assessee sustains a loss of profits or gains in any year under any of the heads mentioned in section 6, he shall be entitled to have the amount of the loss set off against as income, profits or gains under any other head in that year Provided that (2) Where any assessee sustains a loss of profits or gains in any year, being a previous year not earlier than the previous year for the assessment for the year ending on the 31st day of March, 1940, under the head profits of business, profession or vocation, and the loss cannot be wholly set off under sub section (1) the portion not so set off shall be carried forward to the following year and set off against the profits or gains, if any, of the assessee from the same business, profession or vocation for that year Provided that By sub section