Simpson's Rule, as used for determining volumes for admeasurement works this way:
Determine the length. Divide it into any convenient even number of equal spaces. The dividing points between spaces are called stations. If you make ten spaces you will have eleven stations numbered 0 through 10. This must be done both horizontally and vertically. Each space length is called "s". Measure the breadth at each station. These breadths are multiplied by factors as follows:
At station 0, multiply by 1. At station 10, multiply by 1. At even numbered stations, multiply by 4. At odd numbered stations, multiply by 2. Add all breadth times factors together. Multiply the sum by the length of the spaces between stations and divide by 3. Lo! you have the area. You the do the same thing for height. Multiply the height answer times the length answer and you will have the volume. Divide the whole weird mess by 100 and you will have gross tonnage. Buy a double roll of wallpaper for these calculations.
I am not being smart-alecky. I am trying to show the absurdity of the entire tonnage admeasurement system. This sort of thing is the reason why we cannot depend on tonnages to gauge the size or capacity of ships and boats.