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POPULAR SCTEl^CE NEWS. 



[June, 1SS9. 



and civilization, and the development of art and sci- 

 ence, such as was attained in the eighteenth cen- 

 tury, before the human mind turned witli intelligent 

 interest to an investigation of the earth beneath, 

 and endeavored to read the record which nature has 

 written in the rocks. Geology was necessarily pre- 

 ceded by an advanced state of the other sciences, — 

 chemistry, zoology, botany, mechanics, and physical 

 geography being required for the pursuit of its in- 

 vestigations and the solution of the problems pre- 

 sented by the crust of the earth. Geology, there- 

 fore, as a science, is entirely modern, belonging to 

 the nineteenth century, and, both with respect to 

 the magnitude and sublimity of its discoveries, and 

 its influence on modern thought, it probably marks 

 one of the most interesting and important stages in 

 the progress of the human intellect. 



Sir John Herschel declared that "geology, in the 

 magnitude and sublimity of the objects of which it 

 treats, undoubtedly ranks in the scale of the sciences 

 next to astronomy." In the study of astronomy', the 

 mind is overwhelmed by the contemplation of 

 limitless space — of "distances that seem ghostly 

 from infinitude." Scarcely less impressive is the 

 thought of the countless ages which geology re- 

 quires for the changes which have taken place in 

 the relatively small portion of the earth's crust to 

 which man has been able to penetrate. 



Geology shows that the configuration of the 

 earth's surface has been remodelled again and again. 

 Valleys, which have been slowly formed, have been 

 filled up again, and then re-excavated ; mountain 

 chains have been elevated, and again depressed ; 

 sea and land have changed places ; wide continents, 

 with their mountain ranges and resplendent rivers, 

 sinking slowly, to become for long ages the bed of 

 the ocean, and again emerging to become dry land. 

 Old rocks, which required many ages for their for- 

 mation, have been gradually worn down, and their 

 materials carried away by rivers, to form new rocks 

 at the bottom of the sea. The oldest rocks known 

 to us have been made with the remains of earlier 

 formations. Similar rocks are being made now ; 

 and it has been truly said, there seems no indication 

 of a beginning and no signs of an end. 



During all these innumerable ages, through all 

 these revolutions, the evidences of which remain in 

 those portions of the earth's crust which are accessi- 

 ble to man, vegetable and animal life have existed 

 on the globe. The physical changes brought about 

 by an alteration of the relative positions of sea and 

 land; by gradual change of climate, from arctic to 

 torrid, or from torrid to arctic, — all the physical 

 changes which for unknown ages have been taking 

 place on the surface of the earth, — have been accom- 

 panied by corresponding changes in vegetable and 

 animal organisms. Organic forms have slowly 

 changed, in obedience to external changes; the old 

 forms have disappeared, and new ones slowly taken 

 their places. A succession of new plants and ani- 

 mals has constantly been going on. Many species 

 and genera are only found in the earlier formations, 

 and others do not appear till many ages later, while 

 some few genera have existed through all the 

 changes known to geologists, and are represented 

 by species living in the present seas. This differ- 

 ence is to be observed between the phenomena of 

 astronomy and those of geology : however vast may 

 be the cycles of time required for the revolutions of 

 the heavenly bodies, the same series of events is 

 ultimately brought about ; whereas, there is no evi- 

 dence of exactly the same changes in geological 

 phenomena, — the new formations are never exactly 

 like the old ; the successive races of plants and ani- 

 mals always exhibit fresh forms and fresh types ; the 

 pre-existing forms are never revived. And so the 

 old world is ever new. 



We know the earth to be a spheroid, about 8,000 

 miles in diameter, and flattened at the poles. It 

 has acquired this figure under the joint influences of 

 gravitation and the centrifugal force resulting from 

 the rotation on its axis. From a nebulous condi- 

 tion, by process of cooling and condensation, it has 

 gradually assumed its present form, its interior part 

 being probably still in a state of fusion, while the 

 outer surface only has become cooled and solidified. 

 The mean density of the earth is about five times 

 that of water, while the rocks on the earth's surface 

 are only about two and a half times as dense as 

 water. It is not to be inferred from this, however, 

 that the earth is solid to its centre. 



Owing to the force of gravitation, all matter tends 

 towards the centre of the earth, and so great is the 

 consequent pressure, that steel at the earth's centre 

 would be compressed to one-fourth its bulk. It has 

 been calculated that water at a depth of 362 miles 

 would be as lieavy as mercury, and atmospheric air 

 at a deptli of 32 miles as heavy as water. It is evi- 

 dent, therefore, that the mean density of the globe 

 does not warrant the conclusion that it is solid 

 throughout its mass. It is probably the expansive 

 force of heat within the earth that renders its mean 

 density only twice as great as that of the solid mat- 

 ter at its surface. 



Geology inquires into the origin and development 

 of the earth's structure, the materials of which the 

 various strata of its crust are composed, and the 

 method of their formation. It seeks to ascertain the 

 mutations of land and sea, the changes of cli- 

 mate, which have occurred in ancient times, and the 

 effects of physical changes on the numerous tribes 

 of plants and animals which, in endless succession, 

 during interminable ages, have inhabited and 

 adorned the globe. 



The generic term rocks is applied to all the' for- 

 mations that compose the crust of the earth, whether 

 hard and crystalline, — like granite or limestone, — or 

 non-crystalline, — like shale, or chalk, or sandstone ; 

 and also to incoherent masses, — such as clay, sand, 

 gravel, and peat. 



Rocks are termed igneous, when formed by the 

 action of fire; sedimentary or aqueous, when formed 

 underwater; and eolian or aerial, and sometimes 

 alluvial, when formed on the land. This last class 

 is represented by soil, by the sand-hills of deserts, 

 and the natural accumulations of debris at the base 

 of clift's and mountains. 



This short article may be concluded by giving a 

 chronological table of the various formations, in the 

 order of their superposition, and divided into four 

 great classes, placing the newest at the top, and the 

 most ancient strata, or series of strata, at the 

 bottom. 

 Pust-Tkrtiary or Quaternary; 



Historical or Recent. 



Pleistocene. 

 Tertiary or Cainozoic: 



Pliocene. 



Miocene. 



Kocene. 

 Secondary or Mesozoic ; 



Cretaceous. 



Jurassic. 



Triassic. 

 Primary or Pal.-eozoic : 



Permian. 



Carboniferous. 



Devonian, and Old Ked Sandstone. 



Silurian. 



Cambrian. 



Laurcntian or Pre-Canibrian. 



«♦> 



SCIENTIFIC BREVITIES. 



Papin, a native of France, and who died in Ger- 

 many in 1694, was the first man to make experi- 

 ments on the power of steam. 



On the Compressibility of Oxygen, Nitro- 

 gen, AND Hydrogen. — Amagat has subjected oxv- 

 gen, nitrogen, and hydrogen gases to pressures up 

 to 3,000 atmospheies. Ite finds that at 1,000 atmos- 

 pheres the compressibility of gases is no greater 

 than that of liquids, and increases similarly witli 

 the temperature. Calling the density of water 

 unity, the density of oxygen under a pressure ot 

 3,000 atmospheres is 1.1054, that of air is 0.SS17, 

 that of nitrogen is 0.S293, and that of hydrogen i^ 

 0.0887. 



Aluminu'm in Vasci'lar Cryptogams. — In a 

 paper contributed to the Royal Society, Prof. A. H. 

 Church states that aluminium is a constant constit- 

 uent of the ash of some species of Lycopodimn. 

 while it appears to be entirely wanting in others. 

 The following genera gave negative results : Eqiii- 

 setum, Ophioglossum, Salvinia, Mnrsilea, Psilotiiui. 

 and Seliif/inella. Among Filices it was found only 

 among tree-ferns, one species yielding as much as 

 13 per cent, of the ash. The alumina in Lycoim- 

 diuiii occurs in combination with organic acids, and 

 may serve to neutralize the acids produced in the 

 plant. 



The Loss of Pressure in Natural Gas Mains. 

 — It has been found that to pipe natural gas a long 

 distance, as from Murrysville to Pittsburg, much of 

 the pressure is lost. In the old eight-inch mains, 

 between the above points, it used to mean a loss of 

 eight poimds per mile, and, as Pittsburg is twentv- 

 two miles from Murrysville by the pipe line, 176 

 pounds of pressure were thus lost. The Philadel- 

 phia Company now uses the "telescope" system in 

 its pipe line, i. e., the diameter of the pipes at the 

 wells is small, but gradually increases as the line 

 approaches the city. This reduces the loss of pres- 

 sure to about three pounds per mile. 



Fall ok Black Snow. — At Aitken, Minn., on 

 April 2d, at 4:45 o'clock, it became so dark that 

 lights were necessary in business houses, and the 

 air was filled with snow that is represented to have 

 been as black and dirty as though it had been 

 trampled into the earth. Six ounces of snow and 

 one-fourth ounce of dirt and sand were found in the 

 bottom of a dish. The dirt is very fine, something 

 like emery, and contains particles that have a metal- 

 lic lustre. This dirty snow fell to the depth of half 

 an inch. The atmosphere at the time presented a 

 peculiar greenish tinge. There was a little wind 

 blowing at the time from the northwest, though 

 there seemed to be considerable wind higher in the 

 air. Solid chunks of ice and sand are reported to 

 have been picked up in various places. 



Origin of the Names Cobalt and Antimony. 

 — Cobalt is commonly said to have been first ob 

 tained by Brandes in 1742, and its name is connected 

 with certain malignant demons which interfered 

 with the work of the miiier. In fact, cobalt was 

 known to the ancients in the days of Theophrastus 

 (though it had not been isolated), and was spoken 

 of as the "male blue," in opposition to the "fem.iK 

 blue," derived from the compounds of copper. The 

 very name cobalt is traced to the Greek. Thus 

 in the "Lexicon Alchemia; Rulandi," we read : 

 "Cobatiorum funuis est kobalt." The expression, 

 "fume of cobathia," is to be found in a passage ol 

 Hermes, cited by Olympiodorus. Even metallic 

 cobalt seems to have been known as early as i6ij. 

 Metallic antimony was also known in ancient Chal- 

 dea long before its reputed discovery by Basil 

 Valentine, a semi-mythological personage. The 

 very name "antimony" is derived, not from its 

 legendary poisonous action upon monks, but from 

 the Arabic "athmoud" or "othmoud." 



