Thus Venus introduces to us another novelty in the economy of worlds, for with a perpendicular axis of rotation she can have no succession of seasons, no winter and summer flitting, one upon the other's heels, to and fro between the northern and southern hemispheres; but, on the contrary, her climatic conditions must be unchangeable, and, on any particular part of her surface, except for local causes of variation, the weather remains the same the year around.
So, as far as temperature is concerned, Venus may have two regions of perpetual winter, one around each pole; two belts of perpetual spring in the upper middle latitudes, one on each side of the equator; and one zone of perpetual summer occupying the equatorial portion of the planet.
But, of course, these seasonal terms do not strictly apply to Venus, in the sense in which we employ them on the earth, for with us spring is characterized rather by the change in the quantity of heat and other atmospheric conditions that it witnesses than by a certain fixed and invariable temperature.
To some minds it may appear very undesirable, from the point of view of animate existences, that there should be no alternation of seasons on the surface of a planet, but, instead, fixed conditions of climate; yet it is not clear that such a state of affairs might not be preferable to that with which we are familiar.

Even on the earth, we find that tropical regions, where the seasonal changes are comparatively moderate, present many attractions and advantages in contrast with the violent and often destructive vicissitudes of the temperate zones, and nature has shown us, within the pale of our own planet, that she is capable of bringing forth harvests of fruit and grain without the stimulus of alternate frost and sunshine.
Even under the reign of perpetual summer the fields and trees find time and opportunity to rest and restore their productive forces.
The circularity of Venus's orbit, and the consequently insignificant change in the sun's distance and heating effect, are other elements to be considered in estimating the singular constancy in the operation of natural agencies upon that interesting planet, which, twin of the earth though it be in stature, is evidently not its twin in temperament.
And next as to the all-important question of atmosphere.

In what precedes, the presence of an atmosphere has been assumed, and, fortunately, there is very convincing evidence, both visual and spectroscopic, that Venus is well and abundantly supplied with air, by which it is not meant that Venus's air is precisely like the mixture of oxygen and nitrogen, with a few other gases, which we breathe and call by that name.

In fact, there are excellent reasons for thinking that the atmosphere of Venus differs from the earth's quite as much as some of her other characteristics differ from those of our planet.

But, however it may vary from ours in constitution, the atmosphere of Venus contains water vapor, and is exceedingly abundant.