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Geology and Natural History. 145 
Il. GEOLOGY AND NATURAL HIsTory. 
to show that the lava-fields of northwestern Europe are examples 
to a large extent of such non-volcanic ejections. 
Professor Geikie first observes that the volcanoes of the Medi- 
vents, like those of Etna, the Aolian Islands, the Phlegrzan fields, 
or the Greek Archipelago ;” and now, the statement that “the 
origin of whose horizontal or nearly horizontal 
interstratified tufas he says he attempted again and again to 
e author next recounts the facts which he had himself 
observed in Western America, and states that these first enabled 
him to understand Richthofen’s descriptions and the basalt-sheets 
of his own country. From his paragraphs we take the following: 
“Never shall I forget an afternoon in the autumn of last year 
region of the Yellowstone and Madison. We had been riding for 
