subject than might be imagined. In the United States there are a number of holes in the ground, dug by greedy man-some of them mines, others wells for oil and gas-which are over half a mile deep. At Wheeling, West Virginia, there is a boring, for oil, three-quarters of a mile in depth; and near Pittsburg is another which has been put down a mile and a quarter-in accurate figures, seven thousand feet. The latter, originally an oil well, was sunk further for gas, and made deeper still later on for purposes of scientific inquiry. In all of these holes careful measurements of temperature at various levels have been made.

Much of this work has been done by the U. S. Geological Survey, one of whose officers, Mr. N. H. Darton, invented for the purpose a peculiar kind of thermometer, encased in heavy glass. This instrument he has dropped into all of the very deep holes, obtaining valuable data in regard to subterranean temperatures. From information secured in this way by him and by other investigators, in Europe as well as in America, accu

A GEYSER CRATER IN YELLOWSTONE PARK.

MT. PELEE IN ERUPTION, JUNE, 1902.

rate estimates have been made respecting the thickness of the earth's crust, which, though formerly supposed to be the same all over, like the rind of an orange, is now known to be much less in some parts than in others.

As a result of such investigations, it is known that the crust of the planet is rather exceptionally thick in the southern portion of the United States, whereas in South Dakota it is comparatively thin. In the latter region the hot core of the globe comes so near to the surface that the artesian wells are tepid-one such well at the town of Pierre supplying a large swimming pool with water at a temperature of ninety-two degrees Fahrenheit. The city of Yankton is only about twelve miles from subterranean fire-almost appallingly close one might think-while the molten rocks are twenty-five miles beneath Philadelphia and New York-a comparison that will serve to illustrate in a sufficiently striking way the variations in the thickness of the rind of the globe.

In places, however, it is much thinner

than in South Dakota. The famous Hot Springs of Arkansas owe their temperature to volcanic heat not far below the surface. In the neighborhood of St. Augustine, Florida, similar conditions must exist, inasmuch as one great hotel in that town, the Ponce de Leon, is able to

In the Lake Superior region there is a great hole in the earth, dug for copper, which is called the Calumet and Hecla mine. It is nearly a mile in depth. In this excavation, remarkable in more ways than one, Prof. Alexander Agassiz, not long ago, made a painstaking series of

temperature observations at different levels-the method he adopted being the curious one of drilling holes in the rocks and inserting in them thermometers. The instruments were allowed to remain from one to three months-the object in view being to ascertain the temperature of the rocks and not of the air in the mine.

At a depth of 4,580 feet, near the bottom of the mine, the temperature was found to be only seventy-nine degrees Fahrenheit-a circumstance which might well have occasioned surprise were the cause not well understood. Many thousands of years ago all of that region was covered by an enormous thickness of glaciers, the cold of which penetrated so deep into the earth that the chill resulting from the refrigeration, so mighty in its scale, remains even to this day! After all, when one comes to think of it, the facts of science. are far more strange and wonderful than any fiction ever evolved by the brain of the

warm its rooms with hot water from artesian wells. But, to find high temperatures close to the skin of the earth, onc should visit the Yellowstone Park, where, in spots, the flames of a literal hell are obviously raging not far below the ground on which the visitor walks. Geysers and boiling springs are among the more conspicuous plutonic phenomena, while in the Fire Hole district the whole country seems to be on fire.

romancer.

For the sake of contrast, put along side of the above statement the fact that in the celebrated Comstock lode in Nevada, the temperature at a depth of only twenty-five hundred feet is one hundred and forty-five degrees! Only four miles down below this mine is evidently a focus of volcanic heat-a mass of molten rocks which, resembling a mighty furnace,

makes the air in the lower levels of the workings so stifling as to be well-nigh insupportable. Indeed the labor of excavating is attended with extraordinary difficulty, cold water being showered from above upon the toilers with drill and pickaxe, in order to enable them to keep at their tasks.

Prof. Hallock, who made a careful investigation of the sub-surface temperatures in parts of the Yellowstone Park, some years ago, has suggested that, if subterranean heat is wanted for industrial purposes, it might be obtained in unlimited quantities in that quarter without much expense for digging. Energy nowadays is transmitted over indefinite distances by wire, in the form of electricity, so that the plutonic resources of the national reservation might be made available for use in Chicago, in San Francisco, or possibly even in New York. But it would probably be cheaper and otherwise more expedient in the long run to sink pipes to subterranean fire in the vicinity of the great industrial centers, even though it be necessary to go considerably deeper.

Of all things that exist in creation fire

tures down below our feet-temperatures, that is to say, hardly inferior to that of the sun itself.

Whence came all this fire? It is a question which nobody can answer satisfactorily, but it affords a most interest

seems to be the most plentiful. Every star that bespangles the glittering path of the Milky Way is a burning sun. The giant planet Jupiter is afire--a small sun not yet extinguished. As for the earth, it is all on fire inside. But, fortunately for ourselves, its rocky crust is an exceedingly poor conductor of heat, so that it seems difficult to realize that there are celestial tempera

ing subject for speculation. Poisson, a famous astronomer, has suggested that in the inconceivable vastnesses of space there may be regions of enormous heat, as well as regions of cold. At the present time the solar system is traveling through a region of cold, in which the normal temperature is what we call absolute zero-four hundred and sixty-three degrees below the zero of the Fahrenheit