rock taken out were piled up in a rectangular mass, such as builders 

 make of the bricks which they intend to use. In doing this apparently 

 superfluous bit of work, I had a definite object in view, having already 

 determined to return the following summer, if it were possible. Not 

 only was there that beast left behind in Twin Buttes, to be got out, but 

 I felt confident that there was much more of the Uintatherium to be 

 found. We could not stay longer, as, for each one of us, our time was up. 



By returning the following season, I could complete the work of 

 excavating those two fine specimens and I could also get some measure 

 of the rate of weathering and rock disintegration in that region. The 

 extremely peculiar type of topography which is called "bad lands" re- 

 quires the presence of two factors; first, a soft, easily destructible rock 

 and, secondly, an arid climate, which prevents the growth of a protec- 

 tive covering of vegetation. The actual rate of weathering is very slow 

 and the holes cut in the taking out of fossils persist for many years, 

 especially if made in steeply inclined surfaces. The soil, which results 

 from the disintegration of the rock, clings to the top and sides of the 

 buttes and, when wet, forms an extremely tenacious mud, which sheds 

 water like a tin roof. In the South Dakota Bad Lands I have seen a 

 tremendous downpour of rain that continued for half an hour and 

 yet penetrated the soil for less than an inch. 



It is this tenacious, waterproof soil which protects the soft rock 

 beneath and greatly retards the work of rock disintegration, and, now, 

 this deep hole and the rockpile beside it would give me a chance to 

 observe the rate of destruction of the unprotected rock. I may here an- 

 ticipate my narrative so far as to say that, when I returned in the 

 summer of 1886, I could hardly believe my eyes; the big cairn had 

 weathered down into a low heap of mud and the even bigger hole was 

 filled up to the brim with rain-washed soil. It was an astonishing result 

 for a single year and showed how important is the protective role of 

 the soil in retarding rock destruction. Were the soil washed away as 

 fast as it forms, the bad land buttes would dissolve like sugar in the rain. 



Just before leaving the Lone Tree camp, we had an amusing experi- 

 ence there. One evening, while we were at supper, a young "cowhand," 

 hardly more than a boy, dropped in and, according to the universal cus- 

 tom of the country, we invited him to join us, which he did as a matter 

 of course. For a while, he was very silent and reserved, but he evidendy 

 had something on his mind and I was curious to see what it would be 

 like. Suddenly, he burst out with: "Say, what's a peterfied man worth?" 

 Seeing that I should not wish to forestall him, he became confidential 



