57 



THE POPULAR SCIENCE MONTHLY. 



all the Catskills, measuring 4,205 feet, and 

 is the hydrographic center of the region, 

 whence the waters run to the northwest by 

 the Esopus, to the northeast by Woodland 

 Creek, to the south by the Rondout to the 

 Hudson, and to the southwest by the Nevi- 

 sink to the Delaware. The geological struc- 

 ture of the group is similar to that of the 

 northern Catskills. Professor James Hall 

 has announced that, after four years of 

 observation, he has detected the existence 

 of four lines of anticlinals, nearly parallel 

 to each other, and running from southwest 

 to northeast, in conformity with the ordi- 

 nary trend of the Appalachian range. Pro- 

 fessor Guyot is willing to acknowledge the 

 fact, but calls attention to the other fact 

 that these axes cross the chains and valleys 

 almost at right angles, " and were probably 

 posterior to the scooping out of the valleys 

 and mountain-chains, on the conformation 

 of which they had so little effect. ... A 

 hypsometric feature, which may refer to 

 this order of facts, is that the three maxima 

 of altitudes above four thousand feet, the 

 Slide Mountain, Hunter Mountain, and Black 

 Dome, are situated in a straight line, trend- 

 ing from southwest to northeast." 



Silicified Forests f the Yellowstone 

 Park. In Bulletin No. 1 of Vol. V. of the 

 "Geological and Geographical Survey of 

 the Territories," Mr. W. H. Holmes gives 

 an account of a most wonderful geological 

 formation, which attains its greatest devel- 

 opment in the valley of the east fork of the 

 Yellowstone River. It occurs in horizontal 

 layers, having an aggregate thickness of 

 fifty-five hundred feet, that is, the whole 

 formation at this point is a little more than 

 a mile in depth. This is filled throughout 

 with the silicified remains of a multitude of 

 forests, many of the trunks of trees that are 

 still to be seen being of very large size. 

 Some of them are prostrate, and from fifty 

 to sixty feet long ; others are upright where 

 they grew, and some of the stumps measure 

 from five to six feet in diameter. One gi- 

 gantic trunk is described that stands twelve 

 feet above the eroded strata about it, and is 

 ten feet iu diameter. This trunk is hollow, 

 but thewoody structure of what remains is 

 well preserved, the rings of growth being 

 clearly defined. The bark on this stump is 



four inches thick, and on its outer surface 

 deeply lined. Scattered through the forma- 

 tions among the trunks is a great variety of 

 vegetable remains, consisting of branches, 

 rootlets, fruit, and leaves. Specimens sub- 

 mitted to Professor Leo Lesquereaux have 

 been identified as follows : Aralia Whitneyi, 

 Magnolia lanceolata, Laurus Canariensis, also 

 new species of Fraxinus, Cornus Alnus, Ti- 

 lia, Diospyros, Pteris, and Fern. The wood 

 is in many cases completely agatized, and 

 cavities which existed in the decayed trunks 

 are filled with crystals of calcite and quartz. 

 The formations are of the "Volcanic Ter- 

 tiary," and composed of fragmentary vol- 

 canic products, breccias, conglomerates, and 

 sandstones, the two former consisting chiefly 

 of basalt. Many are of great size, and are 

 cemented together in enormous masses or 

 heavy beds by tufaceous and other fine- 

 grained material. These beds or layers rep- 

 resent successive formations, arising from 

 the subsidence of the land, during the inter- 

 missions of which the forests grew. The 

 beds have evidently been changed by the 

 action of water ; and the conclusion is that 

 the formation represents the shore or mar- 

 gin of a great Tertiary lake. It is believed 

 that the beds cover or have covered an area 

 of over ten thousand square miles. 



Germs of Disease in Water. Professor 

 Huxley, in a recent discussion of a paper by 

 Dr. Tidy on water for dietetic purposes, said 

 that diseases caused by what people not 

 wisely call germs are produced invariably 

 by bodies of the nature of bacteria. These 

 bodies could be cultivated through twenty 

 or thirty generations, and then, when given 

 under the requisite conditions, would inva- 

 riably cause their characteristic disease. 

 Bacteria are plants, and we know under 

 what conditions they can live and what they 

 will do. They can be sown and will thrive 

 in Pasteur's solution, just as cress or mus- 

 tard in the soil ; and, if a drop of this solu- 

 tion were placed in a gallon of water, Pro- 

 fessor Roscoe thinks it doubtful if there is 

 any known method by which its constitu- 

 ents could be estimated. Every cubic inch 

 of such water would contain fifty thousand 

 to one hundred thousand bacteria, and one 

 drop of it would be capable of exciting a 

 putrefactive fermentation in any substance 



