Figures 1 and 2 from "Periods Of 25 Variable Stars In The Small Magellanic Cloud," Harvard College Observatory Circular 173. Figure 1 shows the relationship between the stars' maximum and minimum magnitudes (apparent brightness) and the periods of the stars, in days. Figure 2 shows the same relationship, but in terms of the logarithm of the period length. Since all the stars in the Small Magellanic Cloud are about the same distance from Earth, the log linear relationship between brightness and apparent magnitude discovered by Miss Leavitt also hold for the stars' absolute brightness, allowing stars of this class to be used as a measuring rod for galactic and intergalactic distances.