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lAtbiftus. 



" STUDIES IN MICROSCOPICAL SCIENCE.' ♦ 



THESE studies ouglit to Bucceed, for they supply n real want — 

 one which, in the case of microscopic study, can fortunately 

 bo supplied. The astronomer cannot, unhappily, semi round 

 specimen planets for study by those who possess telescoj)e8 of sufti- 

 cicnt power. Nor can the chemist or geoloRist conveniently sendi 

 out geological or chemical specimens for examination. But it is 

 possible to send microscopic subjects, and this is whst Mr. 

 Cole propcfos to do — viz., to issue weekly for the use of 

 students, teachers, the medical profession, and others, micro- 

 scopical preparations, tofiether with linely-executed lithographs 

 of the specimens thus sent out for observation. The iii-st 

 specimen is one of yellow fibro-cartilage from tho pinna of 

 a cow's ear, stained doubly in logwood and resin ; it is shown in 

 the lithograph magnified 33 times linear. Tho methods of stain- 

 ing are charmingly described, and the explanation of the structure, 

 shape of cells, matrix, and other features of tho specimen may be 

 relied on as thoroughly accurate. In Number Two, the subject foi- 

 illustration is a transverse section (through tho interno'ie of tho 

 stem of a first year's twig) of the copper beech, stained in carmine 

 and iodine green, and magnified 25 diameters in tho illustration. 

 The bibliography of the subject is in each case very full. The- 

 work is thoroughly sound and good, and will delight practical 

 microscopists. 



LAND AND WATEll. 



ALL the fossil-bearing rocks on the globe have been formed from 

 the sediment brought down by rivers to the sen, and this 

 sediment has been worn off from the hills and valleys and plains of 

 ancient continents. In recent years it has been attemjited to calcu- 

 late the amounts of sediment worn off by various great rivers from 

 tho surface of the regions drained by them ; and tho results arc- 

 very interesting and instructive. The Slississippi, for ersample,. 

 draining a country with scanty rainfall, and having its sources in 

 the Alleghanies and the Rocky Jlountains, where there are no- 

 glaciers, performs its work of denudation slowly. The Mississippi 

 wears off from the vfhole immense area drained by it about one foot 

 in 6,000 years; while the Po, on the other hand, having its sources 

 in the glaciers of the Alps, works with great rapidity, and lowers 

 the area drained by it at the rate of one foot in 72il years. The 

 mean rate of denudation over the globe seems to be not far from 

 one foot in 3,000 years. Now at this rate, and from tho action of 

 rivers alone, it would take only two million years to wear the whole 

 existing continent of Europe, with all its huge mountain masses,. 

 do\Tn to the sea-level, while North America, in similar wise, would 

 be washed away in less than three millions. 



But while the raindrops, rushing in rivers to tho sea, are thos 

 with tireless industry working to obliterate existing continents- 

 their efforts are counteracted, here and there, and with more or less 

 success, by slow upward thrusts or pulsations from the earth's 

 interior, which gradually raise the Hoors of continents. Thegenei-aV 

 result of the struggle has been that, ever since the earliest geological 

 periods, the surfaces of the great continents now existing have besr.- 

 subject to irregular oscillations; now partially or almost entirely 

 disappearing beneath the sea, now recovering ground as archi- 

 pelagos, or rising high and dry to great elevations, as in the case of 

 Africa. The oscillations have not ortlinarily exceeded from 6,000 t<> 

 10,000 feet in vertical extent. There is no reason for supposing 

 that the general relative positions of the great continents and greftt 

 oceans have altered .at all since the beginning of tho Laurentiaii 

 period. Since life began on the earth there is no reason for supposing 

 that the bottoms of the stupendous abysses which hold the waters 

 of the Atlantic, the Pacific, and the Indian oceans have ever beeib 

 raised up so as to become dry land. Once geologists thought other- 

 wise, and land was turned into sea and sea into land by facili 

 theorisers, as often as it was supposed to be necessary to account 

 for the distribution of certain li-^ards or squirrels, or for changes in 

 climate, such as have left marks behind in many parts of the earth. 

 The greatest physical geologists now living, however — such as llr. 

 Croll and the brothers (icikio — .are convinced that there has been 

 no considerable change in the positions of the great oceans from 

 the very beginning; and this view is ably .sustained by Mr. W.allace 

 --who is probably the highest living authority on the distribution 

 of plants and animals — in his profound and fascinating treatise on 

 "Island Life," lately published. — Mr. Fieke, in the Atlaniic Monihl,'. 



• " Studios in Microscopical Science." 

 F.R.M.S. (Bailliere, Tindall, & Co.) 



By Arthur C. Cole. 



