Now all known substances are "transparent" to gravitation. You can use

screens of various sorts to cut off the light or heat, or electrical

influence of the sun, or the warmth of the earth from anything; you can

screen things by sheets of metal from Marconi's rays, but nothing will cut

off the gravitational attraction of the sun or the gravitational

attraction of the earth. Yet why there should be nothing is hard to say.

Cavor did not see why such a substance should not exist, and certainly I

could not tell him. I had never thought of such a possibility before. He

showed me by calculations on paper, which Lord Kelvin, no doubt, or

Professor Lodge, or Professor Karl Pearson, or any of those great

scientific people might have understood, but which simply reduced me to a

hopeless muddle, that not only was such a substance possible, but that it

must satisfy certain conditions. It was an amazing piece of reasoning.

Much as it amazed and exercised me at the time, it would be impossible to

reproduce it here. "Yes," I said to it all, "yes; go on!" Suffice it for

this story that he believed he might be able to manufacture this possible

substance opaque to gravitation out of a complicated alloy of metals and

something new--a new element, I fancy--called, I believe, helium, which

was sent to him from London in sealed stone jars. Doubt has been thrown

upon this detail, but I am almost certain it was helium he had sent him

in sealed stone jars. It was certainly something very gaseous and thin.

If only I had taken notes...

But then, how was I to foresee the necessity of taking notes?

Any one with the merest germ of an imagination will understand the

The First Men In The Moon