brought to the building and fixed in its place by machinery. It can be tinted to the taste of the purchaser; but, as a rule, a tintless crystal is preferred. 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_. Two periods of the same length before and after noon and midnight are distinguished as the first and second dark, the first and second mid-day zyda. There remain four intervals of three hours each, popularly described as the sleeping, waking, after-sunrise, and fore-sunset zyda respectively. This is the popular reckoning, and that marked upon the instruments which record time for ordinary purposes, and by these the meals and other industrial and domestic epochs are fixed. But for purposes of exact calculation, the day, beginning an hour before mean sunrise, is distributed into twelve periods, or antoi, of a little more than two terrestrial hours each. These again are subdivided by twelve into periods of a little more than 10m., 50s., 2½s., and ⁵⁄₂₄s respectively; but of these the second and last are alone employed in common speech. The uniform employment of twelve as the divisor and multiplier in tables of weight, distance, time, and space, as well as in arithmetical notation, has all the conveniences of the decimal system of France, and some others besides due to the greater convenience of twelve as a base. But as regards the larger divisions of time, the Martials are placed at a great disadvantage by the absence of any such intermediate divisions as the Moon has suggested to Terrestrials. The revolutions of the satellites are too rapid and their periods too brief to be of service in dividing their year of 668⅔ solar days. Martial civilisation having taken its rise within the tropics—indeed the equatorial continents, which only here and there extend far into the temperate zone, and two minor continents in the southern ocean, are the only well-peopled portions of the planet—the demarcation of the seasons afforded by the solstices have been comparatively disregarded. The year is divided into winter and summer, each beginning with the Equinox, and distinguished as the North and South summer respectively. But these being exceedingly