Weather conditions must also be taken into account; head winds may prevail, rendering the forward speed of the ship to be small even with the engines running full out. In calculations it is considered that the following assumptions should be made: 1. At least 75 per cent additional petrol to be carried as would be necessary for the passage in calm air, should unfavourable weather conditions be met. This amount could be reduced to 50 per cent in future airships with a speed of upwards of 80 miles per hour. 2. About a quarter of the total discharge able lift of the ship should be in the form of merchandise or passengers to render the project a reasonable commercial proposition. We will consider the commercial loads that can be carried by the German airship L 70 and our airships R 33 and R 38 under the conditions given above. Two speeds will be taken for the purposes of this comparison: normal full speed, or about 60 miles per hour, and cruising speed of 45 miles per hour. L 70.--At 60 miles per hour a distance of 3,000 miles will be accomplished in 50 hours. Fuel consumption about 13 tons + 9.75 tons (additional for safety) = 22.75 tons. Available lift for fuel and freight = 27.8 tons. Fuel carried = 22.75 " ------------ Balance for freight = 5 " about. ----------- At 45 miles per hour, distance will be accomplished in 66.6 hours. Fuel consumption about 10 tons + 7.5 tons additional = 17.5 tons. Available lift = 27.8 tons Fuel carried = 17.5 " ------------ Balance for freight = 10 " about. ------------ R. 33.--At 60 miles per hour. Fuel consumption 14.25 tons + 10.68 tons additional = 24.93 tons. Lift available for fuel and freight = 21.5 tons. Fuel carried = 24.93 " ------------ Minus balance = 3. 43 " ------------ At 45 miles per hour. Fuel consumption 9.66 tons + 7.23 tons (17 tons approx.) Lift available for fuel and freight = 21.5 tons. Fuel carried = 17 " ------------ Balance for freight = 4.5 " ------------ R. 38.-Estimated only. At 60 miles per hour. Fuel consumption 20 tons + 15 tons additional = 35 tons.