In much laboratory work simultaneous observations are made on two dependent quantities, all others being kept constant. A relation is then sought between these quantities. One of the first recourses is to logarithmic and semi-logarithmic plotting. By dimensional reasoning, relations involving other quantities may then often be inferred, even without further experimentation. A device that combines speed, accuracy, and simplicity for this sort of plotting is therefore desirable as a laboratory adjunct.
In this paper the theory of logarithmic and semi-logarithmic plotting is reviewed, and a device is described which, it is thought, meets the above demands.
The theory of power and exponential finding, especially as the inverse of logarithmic and semi-logarithmic plotting, respectively, is also reviewed, and a simple addition to the above apparatus is described, by which one can read powers and exponentials.
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