“Are you ready for another tramp?” was Andrew Hall’s greeting when we met early on the morning following our return from the peak.

“Certainly I am. What is your programme for to-day?”

“I wish to test the flying qualities of a kite which I have constructed since our return last night.”

“You don’t allow the calls of sleep to interfere very much with your activity.”

“I haven’t much time for sleep just now,” replied Hall, without smiling. “The kite test will carry us up the flanks of the Teton, but I am not going to try for the top this time. If you will come along I’ll ask you to help me by carrying and operating a light transit I shall carry another myself. I am desirous to get the elevation that the kite attains and certain other data that will be of use to me. We will make a détour towards the south, for I don’t want old Syx’s suspicions to be prodded any more.”

“What interest can he have in your kite-flying?”

“The same interest that a burglar has in the rap of a policeman’s night-stick.”

“Then your experiment to-day has some connection with the solution of the great mystery?”

“My dear fellow,” said Hall, laying his hand on my shoulder, “until I see the end of that mystery I shall think of nothing else.”

In a few hours we were clambering over the broken rocks on the south-eastern flank of the Teton at an elevation of about three thousand feet above the level of Jackson’s Hole. Finally Hall paused and began to put his kite together. It was a small box-shaped affair, very light in construction, with paper sides.

“In order to diminish the chances of Dr. Syx noticing what we are about,” he said, as he worked away, “I have covered the kite with sky-blue paper. This, together with distance, will probably insure us against his notice.”

In a few minutes the kite was ready. Having ascertained the direction of the wind with much attention, he stationed me with my transit on a commanding rock, and sought another post for himself at a distance of two hundred yards, which he carefully measured with a gold tape. My instructions were to keep the telescope on the kite as soon as it had attained a considerable height, and to note the angle of elevation and the horizontal angle with the base line joining our points of observation.

“Be particularly careful,” was Hall’s injunction, “and if anything happens to the kite by all means note the angles at that instant.”

As soon as we had fixed our stations Hall began to pay out the string, and the kite rose very swiftly. As it sped away into the blue it was soon practically invisible to the naked eye, although the telescope of the transit enabled me to follow it with ease.

Glancing across now and then at my companion, I noticed that he was having considerable difficulty in, at the same time, managing the kite and manipulating his transit. But as the kite continued to rise and steadied in position his task became easier, until at length he ceased to remove his eye from the telescope while holding the string with outstretched hand.

“Don’t lose sight of it now for an instant!” he shouted.

For at least half an hour he continued to manipulate the string, sending the kite now high towards t............