In the late 1870s the government clerk from Wellington, New Zealand, Leonard Stowe (see biography of Leonard Stowe) devised an adding machine, which he patented in 1880 in Great Britain and Germany (patent Nr. DE11907). The English patent for Stowe's Patent Calculating Machine (see the lower patent drawing) was assigned to Stowe brothers, London.
The patent drawing of Leonard Stowe's adding machine
The machine of Stowe consists of a number of cylinders, or rollers, with figures printed thereon, zero or naught being represented by a red square. To the left of the cylinders are a number of indicators, each of which records every perfect revolution of its corresponding cylinder.
To place the machine ready for work the indicators must be turned until zero or naught is visible; and the cylinders must be turned so that the zero on the extreme left i.e., nearest to the indicators is visible.
Let's see an example.
To add the following figures:
Turn the cylinder towards you till 4 appears in the first column at the left end—stop, start again from the Zero or Red Square, now visible till you come to 5 in that column; start again from the Zero or Red Square, now visible, till yon come to 7 in that column; start again from the Zero or Red Square, now visible, till you come to 3 in that column; start again from, the Zero or Red Square, now visible, till you come to 4 in that column.
On looking at the indicator you will find figure 2 recorded, and figure 3 will be the figure now visible at the left end of the cylinder, the two together making 23 which is the required total.
Note: The result of any addition will always be found by reading the figures recorded on the indicators together with the first figure on the left end of the cylinders.