That section so far as material for our purpose reads as follows : "24(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 his income, profits or gains under any other head in that year: Provided that in computing the profits and gains chargeable under the head 'Profits and gains of business, profession or vocation, any loss sustained in speculative transactions which are in the nature of a business shall not be taken into account except to the extent of the amount of profits and gains, if any, in any other business consisting of speculative transactions: (2) Where any assessee sustains a loss of profits or gains in any year, being a previ ous year not earlier than the previous year for the assessment for the year ending on the 31st day of March, 1940, in any business, profession or vocation, and the loss cannot be wholly set off under sub section (1), so.