Commodities like wool, tobacco, etc. gain in weight due to the absorption of sea-water, therefore, in arriving at the sound value of the damaged cargo such increase in weight must be determined and deducted from the damaged weight. This may be ascertained by comparing the weight of sound cargo and the weight of the damaged cargo. If part of goods arrive sound then an comparison between shipped and delivered weights can be made. If the whole shipment is so damaged increase in weight becomes unascertainable. In such cases rules of Practice offer guidance. E-4: Allowance for water and/or impurities in picked cotton: When bales of cotton are picked, and the pickings are sold wet, the allowance for water in the pickings (where there are no means of ascertaining it) is by custom, fixed at one-third. There is a similar custom to deduct one-sixth from the gross weight of picking or country damaged cotton to take account of dirt, moisture and other impurities. E-5 Allowance for water in cut tobacco: When damaged tobacco is cut of, the allowance for water in the cutting is one-fourth if the actual increase cannot be ascertained.