FIRST GRADE SPRING WORK 67 



Test the hardness and fracture of these stones, and learn for 

 what each kind is used. 



What kinds are too hard to be shaped easily ? Which ones 

 are too soft for foundation? Mention some that are soft 

 enough to be cut readily with stone chisels, yet hard enough 

 to be used for steps or foundations to buildings. 



Visit a limekiln, stone quarry, or marble works and see 

 how these stones are obtained and prepared for use. 



Notice the colors of the different kinds. Strike two stones 

 together and see if any odor is emitted. Which kinds are 

 used in building houses? For what parts of a house are 

 they used ? 



Where are building stones obtained ? Describe or visit a 

 quarry, and explain how rocks are split open with great accu- 

 racy by drilling holes in rows along the line where it is de- 

 sired to split the rock and by putting into these holes slips and 

 wedges. What stones have a grain or cleavage? Which 

 stones break equally well in any direction? Is this an ad- 

 vantage or disadvantage in building stone? Why? Visit a 

 stone yard or marble works, and see how stones are cut, chis- 

 eled, dressed, polished, etc. 



LESSON XXXIX 

 COMMON ROCKS (Continued) 



What is the chief use of limestone in building a house? 

 Break off a splinter of blue limestone, and with a flame and 

 blowpipe burn it until it becomes lime, if possible. Moisten 

 it and note the change it undergoes. Visit a limekiln and 

 see how lime is burned on a large scale. 



Test stones by putting small fragments of them into acid. 

 Strong vinegar will answer, but hydrochloric acid is better. 



