Somebody must have been here just ahead of us. Isn't that a dark glove over there? We come closer. What at a distance seems to be a glove proves to be a hole in the ice so deep it looks dark. Lying flat and carefully peering over the edge we look into something strangely beautiful--an ice palace, with icicles in fantastic groups hanging from the roof. Through this roof the sun comes in delicate floods of pale green light, the combination of the yellow rays with the blue of the ice. We drop pebbles into the hole. They rattle down and down with long, dull echoes, dying away. We can hear the murmur of running water. Gusts of cold air come up that bite like the wind on a sharp winter day. These underground palaces of art start as great cracks in the ice, called "crevasses," from a French word meaning a crevice. They can usually be seen plainly as yawning chasms, but sometimes are so bridged over by the snows that a small, dark hole is all you see. And we might not see that in time. This would be very bad, for these snow bridges are often quite thin. One might like to go down in a crevasse and explore about in this beautiful dream world--but not when one wasn't looking! Even when one _is_ looking and is as careful as can be it's dangerous. But still you may be sure that the famous men who have studied glaciers have done it, for every true man of science likes to get at the bottom of things. It was Agassiz who first went down in this way into the heart of a glacier. It was while he was making his studies in the Alps, and he came very near being drowned in one of the streams that always flow at the bottom of a crevasse, for these crevasses, breaking up the ice, increase the rate of melting. (You know broken ice will not keep so well as a big block.) [Illustration: WHAT TWO BOYS SAW IN THE FAIRYLAND OF ICE When you have read John Muir's story of how he climbed down into a crevasse in California in his shirt-sleeves (see H. & S.) you will know that he was the other of the "two boys" I refer to, one of them being Louis Agassiz, whose adventure in this fairy iceland down in the glaciers is told in this chapter. Don't look dangerous at a distance, do they, those crevasses? Remind one of the crimps in a Christmas pie. But notice the difference when you get up close to one of them in the next picture. ] BUT THESE SCIENTISTS WILL BE BOYS