Decembee 4, 1896.] 



SCIENCE. 



817 



sent the filling of holes made by burrowing 

 animals or by the roots of trees. In places 

 there are thin sheets of lime carbonate, 

 which have been concentrated by water 

 from the loess above and deposited in the 

 cracks in the ash. 



Deposits near Edison. The ash of this 

 region is four or five miles south of the 

 station. The exposures are but two in 

 number, but much larger than those near 

 Ingham. Their general relations are the 

 same. Where the wall of the valley is 

 steep or vertical the ash appears, but 

 where the slope is gentle, as where the 

 loess has slidden down from above, it was 

 not exposed. The larger of the two expo- 

 sures near Edison extends along the side of 

 the valley for a distance of several hundred 

 yards, interrupted here and there by a mass 

 of loess which has slumped, locally con- 

 cealing it. The thickness of the bed is in 

 places more than twenty feet. The ash 

 is more uniform in texture than that near 

 Ingham, there being none so coarse as the 

 coarsest at that point. It seemed to be 

 equally free from foreign matter. A re- 

 entrant in the side of the ravine in which 

 the main exposure occurs, shows that the 

 ash runs back from the wall of the ravine 

 where the main exposure occurs, in undi- 

 minished thickness. 



The second exposure near Edison is about 

 a-half mile from the first and in another 

 valley. The exposure is much less exten- 

 sive than the first laterally, though nearly 

 as thick. It is very probable that the ash 

 is continuous between the two ravines in 

 which it is exposed. 



Deposits near Orleans. The best of the 

 exposures in this locality is near the head 

 of a small ravine tributary to the valley of 

 the E-epublican river. Its general relations 

 are identical with those of the ash at the 

 other localities. As there, it is covered by 

 loess, and as there, it appears only where 

 the valley slopes are steep and where the 



loess has not slumped. The exposed part 

 of the deposit here varies in thickness from 

 five to twelve feet, and the ash is very fine 

 and white. 



Ash in lesser quantities was seen at sev- 

 eral points in the vicinity. In some cases, 

 especially where thin, it is more or less 

 mixed with earthy matter. 



At most of these places the ash showed 

 more or less evidence of stratification ; but 

 in the faces exposed in 1894, the stratifica- 

 tion was not of such a character as to make 

 it altogether certain that the ash was de- 

 posited in water. If deposited in water, it 

 must have been at a time when this region 

 was covered with a lake, presumably a late 

 Tertiary lake, to which the wind brought 

 the ash. So far as the relationships of the 

 ash were seen, it was only clear that the ash 

 was deposited, and probably somewhat 

 eroded, before the deposition of the loess, 

 and__that the loess was deposited before the 

 vallej's in the banks of which the ash is ex- 

 posed were excavated. 



It has long been known that volcanic 

 ash exists in other localities in Nebraska. 

 Some of these were noted long since by 

 Prof. Todd and Mr. Merrill, but, so far as I 

 am aware, no publication has been made of 

 the ash at the localities here mentioned. 

 It may be of interest to add that the vol- 

 canic ash from this region has already be- 

 come an important article of commerce, 

 under the name of pumice. It has been 

 found to be available for all the various 

 uses to which pulverized pumice is put. 

 EoLLiN D. Salisbury. 



University of Chicago. 



THE 3I0DEBN VERSION OF THE LAW OF 

 SUPPLY AND DEBIAND. 



A MOST interesting illustration of what 

 the writer has called ' The Modern Version 

 of the Law of Supply and Demand ' is seen 

 in recently published statistics of the cop- 

 per production of Lake Superior, given out 



