CARBONIFEROUS PERIOD 



1180 



CARBUNCLE 



shown in maps accompanying the article COAL. 

 Modern research leads to the opinion that the 

 eastern and western coal fields were formerly 

 connected but were later separated by erosion; 

 that is, the waters which rushed down the 

 Mississippi Valley carried away the coal and 

 thus separated these fields. The coal measures 

 cover only a small part of the Carboniferous 

 System. In Europe coal measures occur in the 

 British Isles, the basin of the Rhine and in 

 other places. Everywhere they are of great 

 thickness. There are extensive coal deposits 

 in China and also in Australia. 



Life. Our greatest scientific interest now 

 is in the plant life of the period, because the 

 coal was formed mostly from these plants. 

 Fossils found in the coal measures show that 

 the plants were similar to our ferns, horsetails 

 and club mosses, but that they were very much 

 larger than any of these forms now in existence, 

 even in tropical regions. Ferns and horsetails 

 grew to the size of trees and club mosses were 

 of gigantic proportions. Not only were the 

 plants of unusual size, but vegetation was more 

 luxuriant than any now known, and growth 

 must have been more rapid than even in the 

 most thriving tropical regions of the present 

 time. 



Animals resembled salamanders, frogs and 

 other forms that lived partially on land and 

 partially in water. Insects were numerous, as 

 also were various kinds of fish, mollusks and 

 crustaceans. No remains of large animals have 

 been found. See FOSSIL. 



Duration. No system of rock of any time 

 enables the geologist to tell how long the Car- 

 boniferous Period continued. It is estimated 

 that a vigorous growth of vegetation will yield 

 annually one ton of dried vegetable matter 

 to the acre, or 640 tons to the square mile. If 

 this annual growth could be continued for 1,000 

 years and all the vegetable matter compressed 

 to the density of coal it would form a seam 

 of coal about six inches thick. At this rate 

 it would take at least 2,000 years to produce 

 a layer of coal one foot thick. But on some 

 of the coal fields the combined thickness of 

 the seams is from 100 to 250 feet. Between 

 the layers of coal are layers of rock whose 

 formation may have required as much time 

 as that of the coal. But as vegetation grew 

 more rapidly than at present, that condition 

 would shorten to some extent the time re- 

 quired. Thus, taking all conditions into con- 

 sideration, geologists estimate the duration of 

 the Carboniferous Period at from 2,000,000 to 



5,000,000 years, a length of time which must 

 be taken for granted rather than fully compre- 

 hended. See COAL; DEVONIAN PERIOD. W.F.R. 



CARBON MONOXIDE, monoks'id, a color- 

 less gas, formed when carbon dioxide is passed 

 through heated carbon. In it the carbon is 

 combined with only half as much oxygen as in 

 carbon dioxide. Its molecule consists of one 

 atom of each element, whence the prefix mon, 

 meaning one. It is very poisonous, and burns 

 with a blue flame. The little blue flame seen 

 in anthracite or charcoal fires is caused by the 

 burning of carbon monoxide. It is found in 

 ordinary illuminating gas, especially in "water 

 gas" (see GAS), which, because of it, is danger- 

 ous to inhale in even the minutest quantities. 

 Carbon monoxide sometimes escapes from coal 

 stoves and furnaces and causes stupefaction and 

 death to whole families. One volume of it in 

 100,000 volumes of air produces symptoms of 

 poisoning, and one volume in 750 of air causes 

 death in half an hour. Although itself odorless 

 and tasteless, its escape from a stove or gas 

 pipe into the air can usually be detected by 

 the odor of the other gases which escape with 

 it. J.F.S. 



CARBORUNDUM, kar borun'dum, a very 

 hard substance used in place of emery and 

 sandpaper as an abrasive (for polishing). Car- 

 borundum is made by mixing in proper propor- 

 tions coke, sand, sawdust and a small quantity 

 of salt, and subjecting the mixture to intense 

 heat in an electric furnace constructed espe- 

 cially for the purpose. It requires about thirty- 

 six hours to complete the process. When it 

 comes from the furnace, carborundum is a mass 

 of coarse crystals that reflect nearly all the 

 colors of the rainbow, but when ground to 

 powder it is gray. The finest powder is used 

 for polishing; coarser grades are used in place 

 of emery. Hones of various degrees of fineness 

 are made from it, the finest being used for 

 sharpening razors and surgical instruments. 

 Carborundum is a chemical compound of car- 

 bon and silicon. It is manufactured in large 

 quantities at Niagara, N. Y. See, also, CORUN- 

 DUM; EMERY. J.F.S. 



CARBUNCLE, kar ' bung k' I, the name now 

 applied to the crimson and scarlet varieties 

 of garnet when cut with a smooth, rounded 

 surface curving outwards. The term comes 

 from a Latin word meaning little coal; the 

 ancients gave the name to any red, fiery stone 

 that glowed in the darkness like a burning 

 coal. Certain ancient Jewish writers held that 

 the ark of Noah received its light from car- 



