VENUS, THE TWIN OF THE EARTH We come now to a planet which seems, at the first glance, to afford a far more promising outlook than Mercury does for the presence of organic life forms bearing some resemblance to those of the earth.

One of the strongest arguments for regarding Venus as a world much like ours is based upon its remarkable similarity to the earth in size and mass, because thus we are assured that the force of gravity is practically the same upon the two planets, and the force of gravity governs numberless physical phenomena of essential importance to both animal and vegetable life.

The mean diameter of the earth is 7,918 miles; that of Venus is 7,700 miles.

The difference is so slight that if the two planets were suspended side by side in the sky, at such a distance that their disks resembled that of the full moon, the eye would notice no inequality between them.
The mean density of Venus is about nine tenths of that of the earth, and the force of gravity upon its surface is in the ratio of about 85 to 100 as compared to its force on the surface of the earth.

A man removed to Venus would, consequently, find himself perceptibly lighter than he was at home, and would be able to exert his strength with considerably greater effect than on his own planet.