106 LIMESTONE, BY \YM. D. MCPHERSON. 



Fossiliferous limestone is wholly only ancient coquina formed ages ago, 

 and oolitic limestone only ancient aeolian limestone. 



Crystalline limestones are usually called marbles, and some of the finer 

 kinds resemble sugar in the fineness of their grains. The crystalline structure 

 can be easily seen by the aid of a magnifying glass. The veins and colors 

 of other kinds in marble are caused by the staining of iron or other metals 

 and mineral?. 



Sometimes other minerals mix with limestone in quantities enough to 

 produce rocks. One of the most common kinds, and one of the most useful, 

 is phosphate rock, composed of carbonate and phosphate of lime; the latter 

 being usually the remains of animal life. This kind of rock is used as a fer- 

 tilizer. Clay mixes also with limestone, also quartz to some extent, dolo- 

 mite, forming dolomitic limestone, and serpentine, forming what is known 

 as green marble or serpentine limestone, 



Nearly all the great caves of the world, like Mammoth Cave in Ken- 

 tucky, are in limestone rock. Though quite a hard and durable stone if kept 

 dry, limestone readily yields to water action. If an earthquake or other 

 earth movement makes fissures through this rock over a wide area of coun- 

 try, the water on the surface of the earth gets in and washes away and 

 dissolves out the marble, and oftentimes we have an underground river. Under 

 favorable circumstances this river continually widens till Ave have a great 

 cave. With granite, the case is different. Fissures are just as often made, 

 but no cave results. The water flows in, but instead of dissolving away the 

 rock to any great extent, all the sediments and salts in solution in the water 

 settle into the fissure or crevice, and we ha\e what is known as a vein. 

 Thus we see that lime rock, the fissure under water action constantly be- 

 comes larger, while in granite and the harder rocks, the same fissure becomes 

 filled with other minerals, firmly cementing the fracture together again. 



Teachers and others who are interested in nature study will do well to 

 consult Mr. Whidden's list of books upon these subjects. See his advertise- 

 ment on the back page of cover. 



With sixteen original members, a society has been organized under the 

 name of the Maynard Chapter of the Newton Natural History Society. A 

 constitution and by-laws have been framed and the year's work planned. 

 The purpose of the society is to follow a systematic course of work to obtain 

 a deeper insight into nature study. New members are desired. 



Thomas Fitzpatrick, Sec. 



