Open main menu

Page:Popular Science Monthly Volume 7.djvu/415

This page has been validated.

the mesas and plateaus farther away from the mountains, but not lower than the flood-plain of the river.

I have endeavored above to explain the relation of the valleys of the Uinta Mountains to the stratigraphy, or structural geology, of the region, and, further, to state the conclusion reached, that the drainage was established antecedent to the corrugation or displacement of the beds by faulting and folding. I propose to call such valleys, including the orders and varieties before mentioned, antecedent valleys.

In other parts of the mountain-region of the West, valleys are found having directions dependent on corrugation. I propose to call these consequent valleys. Such valleys have been observed only in limited areas, and have not been thoroughly studied, and I omit further discussion of them.

In many cases, there can be no doubt that the present courses of the streams were determined by conditions not found in the rocks through which the channels are now carved, but that the beds in which the streams had their origin, when the district last appeared above the level of the sea, have been swept away. I propose to call such superimposed valleys. Thus the valleys under consideration, if classified on the basis of their relation to the rocks in which they originated, would be called consequent valleys; but, if classified on the basis of their relation to the rocks in which they are now found, would be called superimposed valleys.



THE season when the attention of the public will be directed to protection from lightning is now approaching, and it is of the utmost importance that correct views in regard to the construction and erection of lightning-rods should prevail. We have in this country a class of men who have devoted themselves to the business of making money out of the fears which thunder and lightning inspire, and it unfortunately happens that the majority of these men care more for the money which they obtain than for the actual protection which they afford to their customers. To them, complicated arrangements, that can be defended with any show of reason, are a most important matter, for, on the ground of greater cost and efficiency, a more liberal harvest is obtained. In this connection there has been no more fertile source of imposition than the fallacy that lightning travels only on the surface of metallic conductors, for it has led to the construction of lightning-rods of which the cross-sections are stars, tubes, and all sorts of complicated devices. A recent note in The Popular Sci-