SCIENCE, INVENTION, DISCOVERY. 



323 



appearance and habits of which are known 

 from the remains, found buried in the rocks 

 of this period. The rocks of this age are the 

 freestones, extensively used for building, sand- 

 stone formations, intersected with ridges of 

 trap of igneous origin, limestone and gypsum, 

 laminated and plastic clays, and chalk beds, 

 containing layers of flint. 



The Mammalian Age was the sixth. The 

 reptiles now dwindled in size and diminished 

 in number, being succeeded by quadrupeds, 

 some of which were much larger than any 

 modern species. The deinotherium, masto- 

 don, megatherium and fossil elephant were 

 among the gigantic animals of this era, while 

 the plants resembled those of the present time, 

 palms, oaks, maples, magnolias, etc., being 

 found in the forests. 



The Age of Man is the last of the seven 

 geologic ages. The huge monsters that gave 

 the preceding period its peculiar character be- 

 came extinct, and were replaced by smaller 

 animals those we see around. Man was 

 created, and invested with dominion over the 

 earth. This is the "era of the finished 

 world the era, also, of man's progress and 

 preparation for another and a higher life." 



Geometry. Its origin is ascribed to the 

 Egyptians ; the annual inundations of the 

 Nile having given rise to it by carrying away 

 the landmarks, and the boundaries of farms. 

 Thales introduced geometry into Greece, about 

 600 B. C. The doctrine of curves originally 

 attracted the attention of geometricians from 

 the conic sections, which were introduced by 

 Ptato about 390 B. C. Euclid's elements 

 were compiled about 280 B. C. Geometry 

 was taught in Europe in the thirteenth century. 

 Books on the subject of geometry and astron- 

 omy were destroyed in England in 1552, being 

 regarded as infected with magic. The science 

 was greatly improved and augmented by Sir 

 Isaac Newton and LaPlace. 



Geysers are intermittent, spouting, hot 

 springs, and have a temperature at the boil- 

 ing point. They are found in Iceland, New 

 Zealand, and in the " National Park " at the 

 head waters of the Yellowstone River in the 

 Rocky Mountains. 



The most celebrated is the Great Geyser of 

 Iceland. It consists of an immense well, or 

 funnel, 10 feet wide at its mouth, and about 

 70 feet deep, surmounted at the surface with 

 a basin 65 feet in diameter and 7 feet deep, 

 formed by the deposit of mineral matter from 

 the water. At intervals it sends up a column 

 of water and steam to the height of 100 feet. 

 More remarkable even than the geysers of Ice- 

 land are some that are found in the ' ' National 

 Park." One, the Giantess, throws water to 



the height of 200 feet. Grasshoppers and 

 other insects, and pieces of wood which fall 

 into the waters, soon become incrusted with 

 quartz, which is held in solution by the water, 

 thus permanently petrifying them. 



Glacial Period is a term used in geology 

 to designate the period when the greater part 

 of the northern hemisphere was enveloped in 

 one great ice-sheet. This period belongs to 

 the post-tertiary or later formations, in the 

 geological succession, and is important in its 

 relations to the general question of the earth's 

 history, and especially to the appearance of 

 man upon the earth. Geologists are generally 

 agreed that long before the advent of man, 

 parts of the northern hemisphere were elevated 

 several thousand feet higher than they are at 

 present, causing the cold of the Arctic zone to 

 extend far southward into present temperate 

 regions, and that a vast glacier rising in the 

 vicinity of Hudson Bay covered the American 

 continent north of the fortieth parallel. The 

 loose soil which covers so large a part of the 

 surface of the northern continent to a depth 

 varying from thirty to one hundred feet, over 

 which lie the vegetable deposits of later ages, 

 is considered by geologists the effects of gla- 

 ciers that in the quaternary or latest geological 

 age slowly moved southward across the coun- 

 try. Upon examination it is found that the 

 erratic bowlders scattered over the western 

 prairies and other northern regions are unlike 

 the native rocks of the same regions, being 

 entirely foreign to the localities where they 

 now appear. Sometimes the nativity of the 

 rock is traced hundreds of miles north of where 

 it now rests, showing that some powerful 

 agency has carried it southward. Again, if 

 the native rock be uncovered and closely ex- 

 amined, it will be observed to be polished and 

 grooved with parallel marks, running north 

 and south, as if chiseled out by some coarse 

 and heavy instrument. These marks are 

 attributed to sharp, hai;d rocks projecting 

 through the lower surfaces of the glaciers. 

 That glaciers do produce such markings is 

 proved by examination of the rocks which 

 the moving ice-fields of Switzerland and other 

 glacial regions have worn and are marking 

 to-day ; also, the general appearance of the 

 loose, unstratified, heterogeneous deposit is 

 similar to that of the moraines that the modern 

 glaciers leave as they slowly melt away. In New 

 York and other Eastern states, the rocks are 

 scratched from a northwesterly direction, in 

 Ohio from a northerly direction, showing in 

 each state the direction of the origin of the 

 glacier. Scotland, Ireland, and the major por- 

 tion of England, were enveloped in this great 

 ice-sheet, and Scandinavia was invested with 



