The entire work of building a large house, from the foundation to the finishing and removal of the metallic frames, occupies from half-a-dozen to eighteen workmen from four to eight days.

This, like most other labour in Mars, goes on continuously; the electric lamps, raised to a great height on hollow metallic poles, affording by night a very sufficient substitute for the light of the sun.

All work is done by three relays of artisans; the first set working from noon till evening, the next from evening till morning, and the third from morning to noon.

The Martial day, which consists of about twenty-four hours forty minutes of our time, is divided in a somewhat peculiar manner.

The two-hour periods, of which "mean" sunrise and sunset are severally the middle points, are respectively called the morning and evening _zydau_.