in the previous figure, but the spaces measure 5 feet instead of 3 feet: so that taking the 8th distance, the divisions on the vanishing line BS measure 40 feet each, and at point O we have 400 feet of distance, but we require 800. So we again reduce the distance to a 16th. We thus multiply the base by 16. Now let us take a base of 50 feet at f and draw line fD to 16th distance; if we multiply 50 feet by 16 we obtain the 800 feet required.
Fig. 92. Honfleur.
The height of the lighthouse is found by means of the vanishing scale, which is 15 feet below and 15 feet above the horizon, or 30 feet from the sea-level. At L we raise a vertical LM, which shows the position of the lighthouse. Then on that vertical measure the height required as shown in the figure.
Perspective of a lighthouse 135 feet high at 800 feet distance.
Fig. 93. Key to Fig. 92, Honfleur.