All the buildings have open spaces or gardens around them, thus securing ample allowance of light and air. Smoke is quite unknown; no noxious gases or vapours are discharged into the atmosphere from any of the factories, but all such emanations which cannot be absolutely destroyed are purified, condensed, or otherwise dealt with within the buildings. Thus the air is always kept pure and wholesome. From this description it will be seen that the planning of a town is very systematic, and that it much resembles a wheel. The hub is the central part of the town; the spokes are represented by the bridges; and the outer rim--a very wide one--contains the outer zones. Besides the gardens there are large open spaces where air-ships have their stations, from whence they can start, or on to which they can descend. The air-ships, also, are usually constructed so that they can descend into the canals, on which they can not only float but be propelled. Many of these town areas are the oases, about which so much has been said, and which, like many other Martian details, have been described as illusions. I only wish we had a plentiful supply of such illusions in our own old country! One of the oases we visited was the Lucus Ascræus, in the northern hemisphere. A large number of canals converge from all directions on to this spot--seventeen of them are marked on our maps--so I expected to find it a place of considerable importance. It is, in fact, a very thriving business and manufacturing place--the Birmingham of Mars, besides being also one of the many centres of government. Like most of the manufacturing towns, it is near the tropical region--because the Martians derive most of their heat and power from solar emanations which they have discovered, and these they store up and transmit to very distant places for use when required. Nearly all the places on Mars to which several canals converge are busy centres of trade and contain large populations. There are numerous large towns near the canals on all the dark areas, differing only in detail from those on the oases, the general plan being the same. I remarked to John that "I thought the towns on the dark areas ought to show as rounded spots slightly darker in tint than the surrounding dark areas. Where several towns were close together they would probably be seen as a single spot, large in area and irregular in shape. It seems strange that, except for a few shown on Professor Lowell's charts, they have not been seen by our astronomers; but perhaps during the present near approach of Mars to the earth some of our keen-sighted observers who possess large instruments may see and take note of many more of these dark rounded spots, as they are very numerous, and new towns are in course of development."