CHAPTER I.-THE MACHINERY OF NATURE. 



1 Nothing perishes in this world, hut things simply vary and change their iorm." Pythagoras. 



As a preparation for the Nature Study of the elementary schools the teacher who would 

 lay a reasonably solid foundation for her work along this line must acquire, first, certain 

 fundamental notions concerning Nature's materials and processes. An elementary knowledge 

 of matter and energy is of prime importance. 



A. Matter. This may be defined as whatever occupies space. A property of all known 

 matter is that it has an attraction for every other particle of matter in the universe (gravita- 

 tion). The strength of this attraction depends upon the amount of matier in the two masses 

 and their distance apart. At the same place upon the earth's surface the amount of matter is 

 proportional to its actual weight; that is, the strength of the attraction which the earth has 

 for it. Consider the weight of bodies raised above the surface of the earth; transferred to 

 other planets. 



All matter is conceived to be made up of very minute particles termed molecules, of 

 unknown shape and which even in solid substances are separated by wide intervals. These 

 molecules are held in position by their mutual attractions (cohesion), such attraction being 

 believed to be different from that of gravitation. What is adhesion ? These molecules are 

 regarded as indivisible by any mechanical means but are conceived to be made up of still 

 smaller elementary particles known as atoms and held together by still another type of attrac- 

 tion known as chemical affinity. These atoms are the units that take part in chemical combin- 

 ations but they are no longer believed to be simple in their structure. They ar^ conceived to 

 be aggregations of " electrons,''' excessively small and in rapid motion. Radio-activity is 

 believed to be due to the escape of these electrons. All matter may be classified under two 

 main divisions; a. elements, b. compounds. The elements, of which there are about eighty 

 different kinds, are those forms of matter which have thus far resisted all efforts 10 separate 

 them into simpler substances. The compounds, of which the number is very great, are those 

 substances in which the molecules are made up of atoms of two or more different elements. 

 Most elements and compounds may exist under three different conditions, between which, 

 however, no sharp distinction can be made. 



1. If the molecules are held more or less rigidly in position, resisting somewhat any effort 

 to displace them, the matter is a solid. If the molecules have a definite, orderly arrangement 

 the solid is crystalline, but if no such order exists it is amorphous in its structure. 



2. If the molecules are capable of moving freely over one another and still cling together 

 more or less the matter is a liquid. The molecules of the same substance in the liquid condi- 

 tion are conceived to be farther apart than when in the solid condition, the molecules them- 

 selves probably remaining identical. 



3. When the molecules of any substance are forced apart sufficiently by any agency 

 cohesion is completely overcome and they tend to separate indefinitely, thus giving rise to a 

 gas. Liquids and gases are grouped together as fluids. Cold and pressure are favorable for 

 the production of the solid condition, while heat and lack of pressure give rise to the gaseous 

 condition. Can gases have weight? Gases which are easily changed back to liquids are called 

 vapors. 



Matter can neither be destroyed nor created by any finite power. Either it has always 

 existed or else it was created from non-matter by DEITY. Matter may be made to undergo a 

 great many transformations, but without any actual loss. Find illustrations. In a closed 

 vessel a given amount of matter will always weigh the same, regardless of the changes that it 

 may undergo. Changes in which the nature of the molecule itself is not affected are spoken 

 of as physical changes. Those in which the composition of the molecule is altered are chemical. 



