"Second: I have studied two of the border-line regions of current we discussed. I have found that in one the power is liberated as a similar attractive force but is focused upon the first object in line with the axis of the bar. As long as the current is applied it remains focused upon that object, no matter what comes between. In the second border-line condition the power is liberated as a terrific repulsion.

"Third: That the copper is completely transformed into available energy, there being no heat whatever liberated.

"Fourth: Most important of all, that the X acts only as a catalyst for the copper and is not itself consumed, so that an infinitesimally thin coating is all that is required."

"You certainly have found out a great deal about it," replied Crane, who had been listening with the closest attention, a look of admiration upon his face. "You have all the essential facts right there. Now we can go ahead and put in the details which will finish up the plans completely. Also, one of those points solves my hardest problem, that of getting back to the earth after we lose sight of it. We can make a small bar in that border-line condition and focus it upon the earth, and we can use that repulsive property to ward off any meteorites which may come too close to us."

"That's right. I never thought of using those points for anything. I found them out incidentally, and merely mentioned them as interesting facts. I have a model of the main bar built, though, that will lift me into the air and pull me all around. Want to see it work?"

"I certainly do."

As they were going out to the landing field Shiro called to them and they turned back to the house, learning that Dorothy and her father had just arrived.

"Hello, boys!" Dorothy said, be