There is another theory about Mars, certainly not so absurd as either of those just named, but scarcely supported by evidence at present--the idea, namely, advanced by a French astronomer, that the ruddy color of the lands and seas of Mars is due to red trees and a generally scarlet vegetation. Your poet Holmes refers to this in those lines of his, "Star-clouds and Wind-clouds" (to my mind among the most charming of his many charming poems): "The snows that glittered on the disc of Mars Have melted, and the planet's fiery orb Rolls in the crimson summer of its year." It is quite possible, of course, that such colors as are often seen in American woods in the autumn-time may prevail in the forests and vegetation of Mars during the fullness of the Martian summer. The fact that during this season the planet looks ruddier than usual, in some degree corresponds with this theory. But it is much better explained, to my mind, by the greater clearness of the Martian air in the summer-time. That would enable us to see the color of the soil better. If our earth were looked at from Venus during the winter-time, the snows covering large parts of her surface, and the clouds and mists common in the winter months, would hide the tints of the surface, whereas these would be very distinct in clear summer weather. I fear my own conclusion about Mars is that his present condition is very desolate. I look on the ruddiness of tint to which I have referred as one of the signs that the planet of war has long since passed its prime. There are lands and seas in Mars, the vapor of water is present in his air, clouds form, rains and snows fall upon his surface, and doubtless brooks and rivers irrigate his soil, and carry down the moisture collected on his wide continents to the seas whence the clouds had originally been formed. But I do not think there is much vegetation on Mars, or that many living creatures of the higher types of Martian life as it once existed still remain. All that is known about the planet tends to show that the time when it attained that stage of planetary existence through which our earth is now passing must be set millions of years, perhaps hundreds of millions of years, ago. He has not yet, indeed, reached that airless and waterless condition, that extremity of internal cold, or in fact that utter unfitness to support any kind of life, which would seem to prevail in the moon. The planet of war in some respects resembles a desolate battle-field, and I fancy that there is not a single region of the earth now inhabited by man which is not infinitely more comfortable as an abode of life than the most favored regions of Mars at the present time would be for creatures like ourselves.