while at another point on the elliptic, it will be farthest from the sun and the south pole nearest. There are two midway points when the two poles are practically equidistant."

"Then the days and nights should be of equal length."

"They are. These are the periods of the equinoxes. The point at which the sun is nearest to the south pole we call the winter solstice, and the opposite point, the summer solstice. The summer solstice is on June twenty-first. At that time the declination of the sun is 23½° north of the equatorial line. It starts to decrease until, six months later, it reaches a minus declination of 23½° and is that far south of the line. The longest day in the northern hemisphere is naturally June twenty-first."

"And the shortest day when the sun has the greatest minus declination."

"Precisely, at the winter solstice. Now to explain what is happening. The year went normally until June twenty-first. That day was of the correct length, about fourteen hours and fifty minutes long. The twenty-second should have been shorter. Instead, it was longer than the twenty-first. Each day, instead of getting shorter as it should at this time of year, is getting longer. We have already gained some thirty-two minutes of sunlight at this latitude. The explanation is that the angle between the equator and the elliptic is no longer 23½° as it has been from time immemorial, but it is greater. If the continuing tilt keeps up long enough, the obliquity will be 90°. When that happens, there will be perpetual midday at the north pole and perpetual night at the south pole. The whole northern hemisphere will be bathed in a continuous flood of sunlight while the southern hemisphere will be a region of cold and dark. The condition of the earth will resemble that of Mercury where the same face of the planet is continually facing the sun."

"I understand that all right, but I am still in the dark as to what is causing this increase of tilt."

"No more than I am, old dear. Herriott keeps babbling about a hidden body which is drawing the earth from its normal axial rotation, but the fool ignores the fact that a body of a size sufficient to disturb the earth would throw every motion of the solar system into a state of chaos. Nothing of the sort has happened. Ergo, no external force is causing it. I am positive that the force which is doing the work is located on the earth itself. Furthermore, unless my calculations are badly off, this force is located on or very near the surface of the earth at approximately the sixty-fifth degree of north latitude."

"How can you tell that, Doctor?"

"It would take me too long to explain, Carnes. I will, however, qualify my statement a little. Either a variable force is being used or else a constant force located where I have said. The sixty-fifth parallel is a long line. The exact location and the nature of that force, we have to find. If it be man-made, and I'll bet my bottom dollar that it is, we will also have to destroy it. If we fail, we'll see this world plunged into such a riot of war and bloodshed as has never before been known. It will be literally a fight of mankind for a place in the sun. Due to its favorable location in the new position of the earth, it is more than probable that Russia would emerge as the dominant power."

"Undertaking to destroy a thing that you don't know the location of and of whose existence you aren't even sure is a pretty big contract."

"We've tackled bigger ones, old dear. We have the President behind us. I haven't made much headway selling my idea to that gang of old fossils who call themselves the council of scientists, but I did to his nibs. Just before that attempt at assassination, I had a chin-chin with him. The fastest battle cruiser in the Navy, the Denver, is to be placed at my service. It will carry a big amphibian plane, so be equipped to assemble and launch it. Bolton will relieve you from the Presidential guard to-day. We sail in the morning."

"Where for, Doctor?"

"I feel sure that the force is caused and controlled by men and I know of but one man who has the genius and the will to do such a thing. That man is Saranoff. Because he must be concealed and work free from interruption, I fancy he is working in his own country. Does that answer your question?"

"It does. We sail for Russia."

"Carnesy, old dear, at times you have flashes of such scintillating brilliance that I have hopes for the future of the secret service. In time they may even show human intelligence. Toddle along now and pay your fond farewells to the bright lights of Washington. Meet me at the Pennsy station at six. We'll sail from New York in the morning."

With the famous scientist and his assistant as passengers, the Denver steamed at her best speed across the Atlantic. As soon as New York harbor was cleared, Dr. Bird charted the course. Captain Evans raised his eyebrows when he saw the course laid out, but his orders had been positive. Had Dr. Bird ordered him to steam at full speed against the shore, he would have obeyed without question.

The Denver avoided the usual lanes of traffic and bore to the north of the summer lane. Not a vessel was sighted in the eight days which elapsed before the Faroe Islands came in sight on the starboard bow. The Denver bore still more to the north and skirted around North Cape five days later. At Cape Kanin she headed south into the White Sea. Surprisingly little ice was encountered. When Captain Evans mentioned this, Dr. Bird pointed out to him that it was August and that the days were still lengthening. Once in the White Sea, the Denver was made ready for instant action. A huge amphibian plane was hoisted in sections from the hold and mechanics started to assemble it. Dr. Bird spent most of his time working on some instruments he had assembled in the radio room.

"This is an ultra-short wave detector," he explained to Carnes. "It will receive vibrations to the lowest limit of waves that we have ever been able to measure. The X-ray is high on the scale and even the cosmic ray is far above its lower limit of detection. We are hunting for an electro-magnet, the largest and strangest electro-magnet that has ever been constructed. Perhaps it would be more accurate to say that we are seeking for a generator of magnetic force. It does not generate the ordinary magnetism which attracts iron and steel, nor the special type of magnetism which we call gravity, but something between the two. It attracts the sun enough to disturb the tilt of the earth's axis, but not enough to pull the earth out of its orbit. Such a device should give out a wave that can be detected, if we get a receiver delicate enough and operating on the right wave length."

He spent hours improving and refining the apparatus, but in the end he confessed himself beaten.

"It's no use, Carnes," he said the day after Cape Kanin faded from view to the north. "Either the apparatus we are seeking gives out no wave that we can detect or my apparatus is faulty. Luckily we have other things to guide us."

"What are they, Doctor?"

"The facts that Saranoff must have easy transportation and a source of power. The first precludes him from locating his station far from the sea-coast and the second indicates that it will be near a river or other source of power. The only Russian points on the sixty-fifth parallel that are open to water transport are the Gulf of Anadyr, north of Kamchatka, and the vicinity of Archangel. I passed up Kamchatka because it would mean too long a haul through unfriendly waters from Leningrad and because there is not much water power. Archangel is easy of access at this time of the year and it has the Dwina river for power. That will be our first line of search."

"We will explore by plane, of course?"

"Certainly. We wouldn't get far on foot,