I ventured near the gravity apparatus and examined it carefully. There was a small thing which looked like the switchboard of a telegraph office. The perforations in it were all in a row, and the ten holes were now filled with little brass pegs, which were suspended from above on small spiral springs. These were evidently the points of communication of the negative current to the framework of the projectile. It certainly would do no harm to pull out one of these pegs, as that would only slightly diminish the current. At least I would risk it. My fingers had scarcely closed upon the brass, when I was given such a violent shock as to be thrown powerfully across the compartment; and had my body weighed anything, my bones would certainly have been broken by the concussion. My arm and shoulder did not recover from the stinging and deadening sensation for some time. I noted the little peg I had pulled out hanging by its spiral spring just above the hole it had filled. It would be worth my life to remove the other nine in the same way. Besides, how would I know when the time came to remove them? My eyes fell upon the two large leaden balls suspended from short copper chains. I had seen these before, but now I thought I understood them. They would swing whichever way gravity attracted. They hung down toward my compartment now, and if we ever passed the dead line, they would hang forward toward Mars. But in the neutral point what would they do? When the gravity of planets neutralized each other, the steel of the projectile would repel these balls towards its centre, which would tend to put them both in the same spot and thus bring them together. Moreover, they would slightly attract each other. Yes, it was quite certain that these had been devised as a Gravity Indicator, and they would tell me when we were approaching a dead line, when we were in it, and when it was safely passed. But all that would do me but little good unless I could manage the currents. I sat thinking this over a long time, when it suddenly occurred to me that the doctor would recognise, even in his delirium, the importance of action when these two balls came together. As soon as they had approached each other, I must lift him up and show them to him. The brain that had made them would know their meaning, and know how to act even in illness! Perhaps I was like a drowning man clutching at a straw; but from the moment I thought of this I believed firmly that the solution of the whole problem would come in this manner. My hopes were ready to hang on the slightest peg. It consoled me to remember some instances where men temporarily insane had been brought to consciousness by impending danger, or by the sight of what last weighed upon their mind.