one universal reflector
...Thoreau's Journal: 20-Jan-1857
At R.W.E.’s this evening, at about 6 P.M. I was called out to see Eddy’s cave in the snow. It was a hole about two and a half feet wide and six feet long, into a drift, a little winding, and he had got a lamp at the inner extremity. I observed, as I approached in a course at right angles with the length of the cave, that the mouth of the cave was lit as if the light were close to it, so that I did not suspect its depth. Indeed, the light of this lamp was remarkably reflected and distributed. The snowy walls were one universal reflector with countless facets. I think that one lamp would light sufficiently a hall built of this material. The snow about the mouth of the cave within had the yellow color of the flame to one approaching, as if the lamp were close to it. We afterward buried the lamp in a little crypt in this snowdrift and walled it in, and found that its light was visible, even in this twilight, through fifteen inches’ thickness of snow. The snow was all aglow with it. If it had been darker, probably it would have been visible through a much greater thickness. But, what was most surprising to me, when Eddy crawled into the extremity of his cave and shouted at the top of his voice, it sounded ridiculously faint, as if he were a quarter of a mile off, and at first I could not believe that he spoke loud, but we all of us crawled in by turns, and though our heads were only six feet from those outside, our loudest shouting only amused and surprised them. Apparently the porous snow drank up all the sound. The voice was, in fact, muffled by the surrounding snow walls, and I saw that we might lie in that hole screaming for assistance in vain, while travelers were passing along twenty feet distant. It had the effect of ventriloquism. So you need only make a snow house in your yard and pass an hour in it, to realize a good deal of Esquimau life.