Page:Popular Science Monthly Volume 27.djvu/578

560 with the rainfall of the district. Mr. Becker proposes a theory that the Comstock fissure taps water-ways leading from the crests of the great range of the Sierra Nevada. Under this theory, if the heat is conveyed to the lode by water from great depths, the variations in temperature are readily explained, by supposing variations in the distribution of the heated water.

Mr. Lord's volume—"Comstock Mining and Miners"—is chiefly historical, and has a peculiar interest in that it describes an episode in the development of one of the most important American enterprises, and relates one of the most wonderful stories in mine working that it has ever been given to tell. The dangers faced by the miners from the extreme heat and other causes are vividly sketched. "The service demonstrates anew how elastic are the limits of human endurance when men are drawn on by some masterful passion. The bounds of possibility then confine their achievements but not their attempts. . . . Death alone has the power to say to miners, ' Thus far shall ye go and no farther! '—for no endurable suffering will bar their progress; nor will the loss of life even make them pause, unless the scourge of heat shall strike them down like a pestilence. Of late years heat has killed strong men in almost every deep mine in the lode, and in some mines the deaths so caused have been frequent." The ultimate effect of this extreme heat on the miner's constitution, even when it does not result in immediate death, is also to be considered; and, besides this, all the ordinary dangers of deep mining exist here in aggravated forms.

although published under the direction of Major Powell, is the eighth volume of the Hayden reports. It contains, first, descriptions of the cretaceous flora, including a large number of new species, some representing rare and very remarkable plants, accompanied with general remarks on the geology of the Dakota group, and on the character of the plants with regard to climate and their affinities with plants of succeeding geological periods. The second part contains a revision of the plants of the Laramie group. The third part reviews the floras of the White and Green River regions, which are separated into two groups. The relations of these plants with the flora of the Gypses of Aix, France, which is generally regarded as of the lowest Miocene or Oligocene, are indicated. The fourth part relates to Miocene plants described from specimens obtained from the Bad Lands, California, and Oregon. The plants of the cretaceous Dakota group, as known mostly from their detached leaves, are striking from the beauty, the elegance, and the variety of their forms, and from their size. The multiplicity of forms recognized for a single species is quite as marked as it might be upon any tree of our forests. In analyzing the leaves by detail, "we are by-and-by forcibly impressed by the strangeness of the characters of some of them, which seem at variance with any of those recognized anywhere in the floras of our time, and unobserved also in those of the geological intermediate periods. Not less surprised are we to see united in a single leaf, or species, characters which are now generally found separated in far-distant families of plants." The flora of the Laramie group (Eocene) is quite distinct from the cretaceous. The Green River group includes the famous Florissante Basin, of which we have already given some account. The Miocene plants, which are described by groups according to where they occur, have not been sufficiently recovered to authorize any reliable conclusion regarding their relative stage in either group.

book, which now appears in a convenient volume of the series of "Globe Readings from Standard Authors," is described in the title-page as "First Lessons in Earth-Lore for Children." It presents, in the form of a pleasing allegory, the workings of the geological agencies that have contributed to the shaping of the globe, and the present appearance of its surface, and their results; the operations being supposed to be performed by a "Madam How," under the direction of a mysterious "Lady Why."