An Afterglow
COPY
Dear Prof. Morse:
You will be interested to know that for an hour last night between eleven and twelve the air was so steady here that my ten-inch telescope put on Mars, not only showed a great wealth of detail but also some of the canals, and at times, only at times, a network appearance of them. I have been at it for three weeks on every fair night, but not until last night was there definite result, though at times the effect was as if there existed markings too evanescent to be made out. I despair of getting another such night in this climate. Perhaps the smoke, and general stirring up by bonfires and fireworks, had temporarily worked the atmosphere to uniformity. At any rate, it did not last more than an hour.
The proof that there is no illusion consists in the fact that only at the moments of very great steadiness could the detail be seen:—canals and all. If the effect were the result of optical illusion, it should have appeared on other nights and on last night it should have been present even when the disc was only fairly steady.
The reality is exactly the contrary. To see this finer detail demands the maximum of steadiness, and therefore the appearance when seen is that of the true markings of Mars.
It is probable that the nights of Mars are cold
71
