FORMS OF MATTER. 27 



of the qualities, that you have written, are essential? 

 That is to say, which of them are necessary to make it 

 sand? If a visitor were to come into the room, and your 

 list of characteristics were read, would he be able to know 

 that you were studying sand? Why? If not, what 

 qualities would you need to add? Why have you written 

 these qualities in the order you have chosen? Do you 

 believe yours is the best order? Why? Are some of the 

 observed characteristics related to others? Can you 

 group your qualities in such a way as to bring together 

 those that are more related? What do you understand 

 by "related" in this connection? 



If you were to rearrange your list, on such a basis as 

 this, in what respect would it differ from your present 

 list?. Would it be a more satisfactory arrangement? 



How many of your qualities would come under the 

 head of "form"? How many under the head of "com- 

 position"? of "optical qualities"? What other heads 

 would be needed in order to include all the other char- 

 acteristics you have mentioned? 



b. Pebbles. Rough and smooth and of various sizes. 

 Treat these just as you did the sand, but do not allow 



any comparison to come into your statements. In other 

 words, study and write of the pebbles as though you 

 had not studied the sand. 



c. Crystals. Study these as above, answering similar 

 questions concerning them. Use as many types of 

 crystals as you can get: quartz, gypsum, iron, lead, etc. 

 Many types of crystals may be made economically by 

 making a saturated solution of certain salts in hot water 

 and allowing the water to cool; or place a small portion 

 of the solution on a glass slide or in a watch-glass and 

 allow the water to evaporate. The following substances 



