ELEMENTARY GENERAL SCIENCE 
 
THE GUIDE 
 
ELEMENTARY 
 GENERAL SCIENCE 
 
 WITH EXPERIMENTS 
 
 BOOK I. 
 
 BY 
 
 PERCY E. ROWELL, M. S. 
 
 \\ 
 
 AUTHOR OF INTRODUCTION TO 
 GENERAL SCIENCE 
 
 BERKELEY. CALIFORNIA 
 PERCY E. ROWELL 
 
 1914 
 ALL RIGHTS RESERVED 
 
TV 
 
 I 
 
 COPYRIGHT, 1913, 1914- 
 BY PERCY E. ROWELL 
 
 Published July. 1913 
 Revised and reprinted August, 1914 
 
 MARIN JOURNAL PRESS 
 
 SAN RAFAEL, CAL., U. S. A. 
 
PREFACE. 
 
 This book, the first of a series of four, is written 
 upon the basis that all science must rest upon the broad 
 foundations of general knowledge. Many of the difficul- 
 ties which have beset science teaching in the grades 
 have been due to the fact that only a small field of science 
 has been taught, and that the field has been too minutely 
 studied. To confine the child of a lower grade to a study 
 of a single group of phenomena, just because he is young, 
 is to deprive him of natural opportunities of learning. 
 There is no reason why all branches of science cannot be 
 learned by children, if the beginnings are but presented 
 according to their way of thinking. General knowledge 
 is not necessarily superficial. 
 
 The science which is most valuable to the child is 
 that which explains the phenomena of the environment 
 the science of common things the science of everyday 
 life. No one branch of science can do this, nor can any 
 one branch of science be properly taught without doing it. 
 A blending of all branches of science, as a means for the 
 best teaching of it in the grades, is inevitable. 
 
 The teaching of science in the grades has been handi- 
 capped by the supposed necessity for elaborate and cost- 
 Iv apparatus. Few of the experiments in this text require 
 even the cheaper apparatus, while most of them do not 
 require anything which really should be called apparatus. 
 The use of common things to illustrate scientific truths 
 
 357633 
 
VI PREFACE 
 
 has also the decided advantage of bringing the science 
 home to the child. He repeats his experiments at home, 
 for he has the "apparatus", and the science becomes his, 
 through the reproduction. 
 
 The experiments, although very simple, do not 
 merely verify the statements of the text, but they elab- 
 orate and add to it. They are often the source of 
 information, and thus the pupils become imbued with 
 the desire for investigation the true scientific spirit. To 
 obtain the best results the pupils should write up their 
 experiments in brief manner and illustrate their work 
 with simple drawings of the apparatus and objects which 
 have been used. 
 
 There has been no attempt at an exhaustive study o\ 
 any one thing. Many of the sections could be enlarged 
 to produce a book in themselves. The attempt has been 
 made, however, to show the balance which exists between 
 vegetable and animal life, and the underlying principles 
 which govern all animate as well as all inanimate exist- 
 ence. If the conditions are such as to warrant the sne- 
 ria.1 and more comprehensive study of any of the sec- 
 n'ons, the List for Teachers, which the United States 
 Department of Agriculture has prepared, should be con- 
 sulted. This list covers a vast field, not alone from the 
 agricultural standpoint, but from that cf general science. 
 
 The work is cumulative, always building upon the old 
 and constantly making use of it. Often the foundations 
 for a section are laid many sections before, and thus the 
 science lessons become one whole, a complete blending 
 of the different parts being accomplished natnrallv. and 
 without apparent effort on the part of the teacher or 
 pupils. 
 
PREFACE VII 
 
 Teaching the applications of science to the industries 
 and the arts will give the pupils the first insight into their 
 own desires and capabilities. They will thus begin un- 
 consciously to prepare themselves along the line of pre- 
 vocational work. Later they will also realize the dignity 
 of labor, and the science teaching may easily develop into 
 the various branches of vocational work, and the pupils 
 may be given the rare opportunity of viewing the field of 
 human endeavor and of truly choosing their career in life. 
 
 Many new texts and other publications have been 
 freely consulted in the preparation of this book. Since 
 much of the material has become common property, 
 specific acknowledgment has not been made, but the 
 author takes this opportunity of thanking the many pub- 
 lishers who have so kindly supplied him with reference 
 books. 
 
 Especial thanks are due Mr. James B. Davidson, 
 Superintendent of Schools of Marin County, California, 
 and Mr. David R. Jones, City Superintendent of Schools 
 of San Rafael, California, both of whom have read the 
 manuscript and have given to the book the benefit of 
 their experience. Thanks are also due Messrs Boggs, 
 Davalos, and Persell who made many of the drawings. 
 Acknowledgement is made through the text for other 
 special obligations. The author alone is responsible for 
 any mistakes which may have crept into the work. 
 
 PERCY ELLIOTT ROWELL. 
 Berkeley, California. 
 Tuly, 1913 
 
CONTENTS 
 
 Section Page 
 
 1. Time of Sunrise and Sunset , . ,. . 1 
 
 2. Experiments . . , . . 1 
 
 3. Direction. The North V . . . . 2 
 
 4. Circular Measurement . . . . . 7 
 
 5. Other Directions . . . ... 8 
 
 6. The Direction of Sunrise and Sunset . .. 10 
 
 7. Telling Time by the Sun . . ' '*' . 12 
 
 8. Other Ways of Telling Time .< '.- . 13 
 
 9. The Height of the Sun at Noon * . \ 15 
 
 10. The Light We Receive from the Sun . . 19 
 
 11. The Sunlight Makes Plants Green ."'.. . .\ 20 
 
 12. Other Changes of Color which are Caused by 
 
 Sunlight . . . .. .' .'. . 22 
 
 13. The Sunlight Good for Plants and Animals 25 
 
 14. Light Travels in Straight Lines 'if- * . 26 
 
 15. The Reflection of Light . . . . 29 
 
 16. Light from Sources Other Than the Sun . 33 
 
 17. The Heat we Receive from the Sun . . 39 
 
 18. Expansion Due to Heat . . .44 
 
 19. The Thermometer an Application of Expansion 48 
 
 20. Heat Produces Light . . ' . . . 53 
 
 21. Heat from Friction . . . / , 54 
 
 22. Heat from Combustion . * . . 58 
 
 23. Combustibles and Fuels . . . . 60 
 
 24. Flames ^ . . . . . . . 62 
 
 25. First Aid to the Burned . . . t . 64 
 
 26. Conduction of Heat 66 
 
X CONTENTS 
 
 27. Air a Necessity of Life . . ... 71 
 
 28. Air in the Soil and in Water . . . . 72 
 
 29. The Composition of the Atmophere . . 75 
 
 30. Oxygen and its Uses ' . .- . . .. .1 78 
 
 31. Nitrogen and its Uses "... .. .. ...... '."'1 8.3 
 
 32. Carbon Dioxide ,. , . . . ... . 81 
 
 33. Respiration. The Necessity for Pure Air . 85 
 
 34. Water is a Liquid . ..... . . . 89 
 
 35. Water can Pass into Some Things .' -. . 91 
 
 36. Solution and its Oddities . " . . . 95 
 
 37. Crystals . ." ... '. .' . . 98 
 
 38. Water for Drinking . - '. ' . . . 100 
 
 39. Water for Cleansing ... ; . ' . 10? 
 
 40. Plants Need Water ' . .-'.-.' -. . 105 
 
 41. Capillarity . . ...;.'. : ,' 106 
 
 42. The Beginning of Plant Life . . . 113 
 4j3. The Testing of Seeds . .' .._^-r''^~\\4 
 
 44. The Proper Planting of Seeds ' .; . . 116 
 
 45. The Needs of the Plant . .. . . .- ' I 118 
 
 45. Birds . . . . . - . . : 120 
 
 47. Wild and Garden Flowers . . . , 122 
 
 48. Trees . . . . . 123 
 
 49. A Queer Plant Yeast , . . .127 
 
 50. Another Queer Kind of Plant The Bacteria 129 
 
 51. Souring and Decay . . 130 
 
 52. Disease and Sanitation . 
 
 53. The Source of All Food .. * '' . 'V 137 
 
 54. The Farm a Workshop . . V . '; 140 
 
 55. Tilling the Soil , . . . . . HI 
 
 56. Irrigation and Drainage of Farms 
 
 57. Gardening .... 14.i 
 
CONTENTS XI 
 
 58. Simple Measurement . . . . . 151 
 
 59. Everything Has Weight. The Balance . 154 
 
 60. Everything Occupies Space . . . . 159 
 
 61. Density . . . . . . ... r . 160 
 
 62. Drawings . . . . . , . . " .-. . 162 
 
 63. Forces .. . . , . , . i . 164 
 
 64. The Plumb-bob and the Pendulum j| ' . / . 167 
 
 65. The Lever . ... -. \ . . 16S 
 
 66. The Inclined Plane , . . " . ' ' : .' 170 
 
 67. The Lodestone . .-...' .. '. '.>; . 174 
 
 68. Steel Magnets . -.. .. , . . 175 
 
 69. Weather Observations ... J. . . 182 
 
 70. How to Make Blue-print Paper - . '. . 183 
 
 71. Solar Heaters . . . . . . . 184 
 
 72. Hot-Air Engines . . , ". , r 185 
 73 Fireproofing . . . . '. . . i 185 
 
 74. Waterproofing .. . ... . . . . ISO 
 
 75. Flavoring Extracts and Perfumes . . . . 187 
 
 76. To Remove Grease Spots and Stains . . 188 
 
 77. How to Make Soap . - . . ,. . 188 
 
 78. Bread Making . .... l^ 
 
 79. Alcohol for Industrial Purposes . . . 190 
 
 80. The Pantagraph . . . . . .191 
 
 81. Levelling .192 
 
 APPENDIX. 
 
 Reference Books on Birds . . ... 195 
 
 Reference Books on Flowers . . . . 195 
 
 Reference Books on Trees . .^ . . . 195 
 
 List of Apparatus and Materials . . : . . 196 
 
LIST OF EXPERIMENTS. 
 
 Section Page 
 
 3. Expt 1. To Locate the North by the North 
 
 Star . ' .' . . ' ;. 3 
 
 Expt. 2. The Movement of the Great Dipper 4 
 Expt. 3. To Locate the North by Means of 
 
 Shadows ." . . . . 5 
 
 5. Expt. 4. To Locate the South by Means of a 
 
 Watch . .... . 8 
 
 6. Expt. 5. The Direction of Sunrise and Sunset 10 
 Expt. 6. To Record the Direction of Sunset 11 
 
 7. Expt. 7. The Sundial , . ... . .12 
 
 8. Expt. 8. The Sand-glass . . ". > ' 14 
 
 9. Expt. 9. The Height of the Sun at Noon by 
 
 by Shadows . . . . 15 
 
 Expt. 10. The Height of the Sun at Noon in 
 
 Degrees . . . . . 16 
 
 10. Expt. 11. The Appearance of the Sun 
 
 through Smoked Glass . .j 19 
 
 11. Expt. 12. The Effect of Sunlight upon Grow- 
 
 ing Plants ' 20 
 
 12. Expt. 13. Fading and Bleaching . ... 22 
 Expt. 14. Blue Prints of Leaves and other 
 
 Articles . . . ; . . 23 
 
 14. Expt. 15. The Way Light Travels . . 26 
 Expt. 16. How to Make and Use a Pin-hole 
 
 Camera . . . . . 27 
 
 15. Expt. 17. Reflection from Mirrors . .29 
 Expt. 18. Diffused Reflection of Light . .31 
 
LIST OF EXPERIMENTS XIII 
 
 16. Expt. 19. Ordinary Sources of Light . . 33 
 Expt. 20. Cold Light .. . . -. . 36 
 
 17. Expt. 21. The Varying Heat from the Sun . 40 
 Expt. 22. The Amount of Heat Received by 
 
 Different Colors . . . . 42 
 
 Expt. 23. The "Burning Glass" . - . 43 
 
 18. Expt. 24. Heat Causes Expansion . . 44 
 Expt. 25. The Result of Unequal Expansion 46 
 
 19. Expt. 26. How to Read a Thermometer .". 50 
 Expt. 27. Hot or Cold? . V >' : - 52 
 
 21. Expt. 28. Primitive Fire-making . . . . 55 
 Expt. 29. The Flint and Steel Gaslighter . 56 
 
 22. Expt. 30. Complete and Incomplete Combus- 
 
 tion . . . -,. . . ' 59 
 
 23. Expt. 31. The Combustion of Different Mate- 
 
 rials .. . . ? :"-:.' -'. -I 61 
 
 24. Expt. 32. The Cause of Flames . -.-;, . r .j 62 
 
 25. Expt. 33. Drill for Extinguishing.. Burning 
 
 Clothing . . . : . . 64 
 
 26. Exot. 34. Good and Poor Conductors of Heat 67 
 
 27. Expt. 35. Holding the Breath and Deep 
 
 Breathing . * . , ; 71 
 Expt. 36. The Effect of Depriving a Plant of 
 
 Air .... > 71 
 
 28. Expt. 37. To Show the Presence of Air in 
 
 Soil and Water . . . .73 
 
 29. Expt. 38. The Amount of Oxygen in the Air 76 
 Expt. 39. The Amount of Carbon Dioxide In 
 
 the Air . 
 
 30. Expt. 40. To Prepare and Use Oxygen . 78 
 32. Expt. 41. Carbon Dioxide from Combustion 
 
 and the Breath ' . 82 
 
XIV LIST OF EXPERIMENTS 
 
 33. Expt. 42. The Capacity of the Lungs ., .- 86 
 
 34. Expt. 43. The Level . . . . , 89 
 Expt. 44. Water Seeks its own Level. Size 
 
 of Drops .'..'- . . . 90 
 
 35. Expt. 45. Porous Bodies Absorb Water . 92 
 Expt. 46. To Make Porous Bodies Waterproof 93 
 Expt. 47. Filtration .- , . . . . 93 
 
 36. Expt. 48. Solution and its Oddities .. .95 
 Expt. 49. The Use of Gasolene and Alcohol 
 
 as Solvents ".'-. . . 97 
 
 37. Expt. 50. Crystallization . . .98 
 
 39. Expt. 51. Hard and Soft Water. Soap . 103 
 
 40. Expt. 52. The Effect of Water upon Seeds 
 
 and Plants . . . . 106 
 
 41. Expt. 53. Examples of Capillarity . ' ; 107 
 Expt. 54. How Water is Held in the Soil . 108 
 Expt. 55. Capillarity in Plants ;...- . .110 
 
 42. Expt. 56. The "Pocket Garden" . . 113 
 
 43. Expt. 57. Germination Tests . . . 114 
 
 44. Expt. 58. The Proper Depth of Planting . 116 
 
 47. Expt. 59. A Flower Collection . . 122 
 
 48. Expt. 60. A "Tree" Collection . 125 
 Expt. 61. Planting Tree Seeds . . 126 
 
 49. Expt. 62. Fermentation 
 
 51. Expt. 63. How to Preserve Milk . , 131 
 
 58. Expt. 64. Measurement 
 
 59. Expt. 65. Making a Balance and Weighing 156 
 
 60. Expt. 66. Displacement of Water by Solids 
 
 and Air . 
 
 61. Expt. 67. Density - 161 
 
 62. Expt. 68. Blue Prints from Tracings . .163 
 
LIST OF EXPERIMENTS XV 
 
 63. Expt. 69. Weighing by Elasticity . ., 165 
 
 64. Expt. 70. The Pendulum ..... 168 
 
 65. Expt. 71. The Use of the Lever . f . .' 169 
 
 66. Expt. 72. The Use of the Inclined Plane . 170 
 68. Expt. 73. Magnetic Materials . . . 175 
 68. Expt. 74. To Draw a Magnetic Field . ., 176 
 68 Expt. 75. Blue Prints of Magnetic Fields . 177 
 68. Expt. 76. Attraction and Repulsion . . . 178 
 74. Expt. 77. Waterproofing . * . . 186 
 77. Expt. 78. Soap Making . . . . 189 
 79. Expt. 79. Making and Distilling Alcohol . 191 
 
THE GUIDE 
 
ELEMENTARY GENERAL SCIENCE 
 
 THE SUN, STARS, AND PLANETS. 
 1. Time of Sunrise and Sunset. 
 
 Did you see the sun rise this morning? Was it too 
 early for you? Does the sun always rise before you do? 
 What time did the sun set last night? Does the sun 
 always set at that time? Watch the time of sunrise and 
 sunset for several days and keep a record of your results. 
 
 The days 'are longer in summer than in winter be- 
 cause the sun rises earlier and sets later than in winter. 
 The longest day of the year is June 21 and the shortest 
 day is December 21. On two days of the year the sun 
 rises at six o'clock in the morning and sets at six o'clock 
 in the evening. These two days are half way between 
 June 21 and December 21. Count the days on a calendar 
 and tell what are the dates of these two days. These 
 days are called the Equinoxes, meaning equal nights. 
 
 You will discover, if you keep a record of the time 
 of sunrise and sunset, that the sun always rises as much 
 before noontime as it sets after noontime. See Experi- 
 ment 3. Thus the forenoon and the afternoon are of the 
 same length. What can you say of the number of hours 
 between sunset and midnight and the number of hours 
 between midnight and sunrise? 
 
 2. Experiments. 
 
 We can learn from teachers and from books or we 
 
 Etem, Sei. 1 
 
2 THE SUN, STARS, AND PLANETS 
 
 can learn from the things themselves. All of our knowl- 
 edge comes from experience with the actual things which 
 have been studied in the past by those who have written 
 books about them. The use of books, then, saves time 
 for we can read in a few minutes the results of years of 
 study. Our teachers also can help us very much because 
 they have learned from other books, from other teachers, 
 and from things. Wherever it is possible we should 
 study things. We may forget what the books say and 
 what the teacher has said, but we can easily remember 
 what we ourselves have done. W 7 henever we try to dis- 
 cover from the thing itself how it acts, we are perform- 
 ing an experiment. 
 
 The best way in which to learn science is by means 
 of experiments, because science is a study of how every- 
 thing acts and why it acts as it does. We may not 
 have our books with us always, and if we can discover 
 from the things themselves what we want to know we 
 shall become independent, and learn without help from 
 books or from teachers. There are many studies which 
 must be learned from books but science is an exception. 
 The record which you are keeping of the time of sunrise 
 and sunset is an experiment. The value of experiments, 
 then, is that we can learn from the very thing what we 
 want to know. 
 
 3. Direction. The North. 
 
 Sometimes it is important to know in what direction 
 you should go in order to arrive at a certain place. In 
 cities and towns the direction can be easily learned from 
 the streets. We are directed to go a certain number of 
 blocks one way and then a certain number of blocks an- 
 
DIRECTION. THE NORTH 3 
 
 other way. On the ocean and in the open country, how- 
 ever, where there are no roads, we must depend upon 
 some other method of finding our way. One method is 
 by means of a star which is so nearly in the north that 
 it is called the North Star. 
 
 Among all the stars which brighten the sky at night, 
 it would be very hard to find the North Star if there 
 were not a huge sign in the sky which always points to 
 it. This sign is called the Great Dipper. The two stars 
 which are the farthest from the handle are called the 
 ''pointers" because they point to the North Star. Let us 
 try to locate the north by the North Star. To do this 
 we shall perform an experiment. 
 
 Experiment 1. To Locate the North by Means of 
 the North Star. 
 
 Materials : Two straight sticks, string. 
 
 a. Look in the sky until you find the Great Dipper 
 Then glance from one "pointer" past the other "pointer" 
 until your glance has gone beyond it five times the dis- 
 tance between the two pointers. There you will see the 
 North Star. When you look at this star you are looking 
 almost exactly north. 
 
 b. If we did not make some record of the direction 
 of the North Star we should be unable next day to tell 
 exactly where the north is. To make a record we need 
 two sticks. Drive one stick into the ground in a place 
 from which the North Star is visible. Then go south 
 from this stick about five feet and drive the second stick 
 into the ground in such a position that by looking just 
 past its edge, you can see the North Star just past the 
 ed<re of the first stick. The two sticks are said to be in 
 
4 THE SUN, STARS, AND PLANETS 
 
 line with the North Star, because if a line were drawn 
 from one stick to the other, and then extended far enough 
 it would pass to the North Star. A string stretched be- 
 tween the two sticks forms a line which points north. 
 
 Review Questions, 1. 
 
 1. When did the sun rise this morning? 
 
 2. How can you tell the time of sunrise by the 
 time of sunset? 
 
 3. Why are books valuable? 
 
 4. What is an experiment? 
 
 5. What are some of the advantages of performing 
 experiments? 
 
 6. When should we use books and when should 
 we experiment? 
 
 7. How do those who write books learn what to 
 write? 
 
 8. How do we direct persons from one place to an- 
 other, in a city? 
 
 9. What must we do in the open country, or on the 
 ocean, to know in what direction we are going? 
 
 10. Why did you drive two sticks in the ground to 
 make a line pointing north? Could you have done it 
 with one stick? 
 
 Experiment 2. *The Movement of the Great Dip- 
 per. 
 
 Apparatus: Rule, scissors, dividers. 
 
 Materials: Cardboard 6"xl2", paper fastener, or 
 pin and piece of cork. 
 
 * See Section 62 before performing this experiment 
 
 J 
 
THE MOVEMENT OF THE GREAT DIPPER 5 
 
 a. Cut the cardboard into two squares 6"x6" and 
 find the center of each piece. To do this lay the rule 
 upon the cardboard so that it crosses it and touches two 
 corners. Make a short line near the center and repeat 
 for the other two corners. Where the two lines meet is 
 the center. Open your dividers so that the points are 
 two and one-half inches apart; place one point upon the 
 center of one piece of cardboard and draw a circle. Upon 
 
6 THE SUN, STARS, AND PLANETS 
 
 this circle draw the Great Dipper and Cassiopeia, as 
 shown in the illustration, and fasten it by means of a 
 paper fastener, or a pin pushed through the centers into 
 a piece of cork. 
 
 b. Hold the apparatus so that you must look toward 
 the north in order to see it. Turn the circular piece so 
 that the Great Dipper is in the position in which you saw 
 those stars at eight o'clock last night, and mark with the 
 date the square piece of cardboard where the line comes 
 which passes through the "pointers." 
 
 c. Look at the Great Dipper at seven o'clock and 
 at nine o'clock. Does it move in the same direction as 
 the hands of a clock or in the other direction? 
 
 d. Look at the Great Dipper once a week for a few 
 weeks, and then once a month, always at eight o'clock, 
 and mark the square piece with the date. See how much 
 of the way around the North Star the Great Dipper goes 
 in one month and then tell where you think the Great 
 Dipper will be in six months. 
 
 Experiment 3. To Locate the North by Means of 
 Shadows. 
 
 Apparatus: Long nail, board. 
 
 a. Drive the nail into a level board placed where the 
 sun will shine upon it all day. Mark along the shadow 
 of the nail at nine, ten, and eleven o'clock, in the morn- 
 ing, and at one, two, and three o'clock in the afternoon. 
 Half-way between the shadows which were cast at nine 
 o'clock and three o'clock is north. Half-way between 
 the shadows cast at ten o'clock and two o'clock also is 
 north. The same is true of the other two shadows. Can 
 you discover some rule in regard to the directions of 
 
CIRCULAR MEASUREMENT 7 
 
 shadows in the forenoon and in the afternoon? Why do 
 you think so many shadows were marked? What would 
 you do if part of the day were cloudy? 
 
 The north side of trees has the most moss, as a rule, 
 because that side receives the least sunshine and is the 
 wettest. Since moss requires a large amount of moisture 
 it cannot live on the sunny side of trees, unless there is 
 a great deal of rain. 
 
 4. Circular Measurement. 
 
 If you stand in one place and turn around until you 
 face the same way as you did before you began to move, 
 you have made one revolution, or a complete circle. If 
 someone told you to turn one-half or one-quarter the way 
 around you would know how far to turn. Perhaps you 
 could turn one-eighth the way around. If someone 
 wanted you to turn one-sixteenth the way around you 
 probably would not know how far to turn. In order to 
 
8 THE SUN, STARS, AND PLANETS 
 
 measure any part of a revolution r or a circle, it has been 
 divided into 360 parts called degrees. A degree means 
 a step. The number 360 was chosen because it can be 
 divided evenly by so many numbers. See if it can be 
 divided by 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12. Try divid- 
 ing 360 by other numbers. A semi-circle divided into 
 180 degrees is called a protractor. It is used to measure 
 the part of a revolution, or circle, which one direction 
 turns from another direction. The short and proper way 
 of writing "degrees" is to use a little circle after the num- 
 ber. For example, 75 degrees may be written 75. This 
 means 75 parts of a circle. 
 
 5. Other Directions. 
 
 If you face the north, the south is behind you ; the 
 east is at your right and the west is at your left. These 
 four points of direction are each a quarter of a revolution, 
 or a quarter of a circle, from the next one. How m^ny 
 degrees between any two of them? How many degrees 
 between the north and the south. If one direction is 181 
 dgrees from another direction the two directions are said 
 to be opposite each other. Is the east opposite to the 
 west? Why? 
 
 Experiment 4. To Locate the South by Means of 
 * Watch. 
 
 a. Hold the watch so that the hour hand points 
 toward the sun. The south direction will then be just 
 half way between the hour hand and the figure XII on 
 the watch. Do this both in the morning and afternoon 
 and see if the result is the same. Can you tell where the 
 north is from this experiment? 
 
OTHER DIRECTIONS 
 
 These four directions, north, south, east, and west 
 
 are not enough 
 for even ordinary 
 use, so the half- 
 way points are 
 named according 
 to the directions 
 between which 
 they come. The 
 directions north 
 and south are 
 named first, thus: 
 North-east, north- 
 west, south-east, 
 and south - west. 
 How many degrees are there between north-east and 
 east? Between north-east and north-west? Between 
 south-east and south-west? 
 
 Review Questions, 2. 
 
 1. Make a drawing of the Great Dipper as it was 
 the last time you saw it, and write the date and hour 
 when you saw it. 
 
 2. How often does the Great Dipper seem to go 
 around the North Star? 
 
 3. Which side of the house is the driest, the north 
 side or the south side? Why? 
 
 4. Is it better to answer the last question after 
 noticing the rooms of a house, or to find the answer in 
 some book? 
 
 5. How many degrees are there in half a circle? 
 In a quarter of a circle? If you are walking along a 
 
10 THE SUN, STARS, AND PLANETS 
 
 street and turn into a side street, how many degrees do 
 you turn? 
 
 6. What is a protractor? For what is it used? 
 
 7. If you face the south, where is the east? The 
 west ? 
 
 8. If you are facing east, how much must you turn 
 in order to face north? Would you turn toward the left 
 or toward the right? 
 
 6. The Direction of Sunrise and Sunset 
 
 Where did the sun rise this morning? Where did 
 it set last night? Does the sun always rise in the same 
 place? Does it always set in the same place? Where 
 would the shadow of a stick point at sunrise? Where at 
 noon? W^here at sunset? An experiment is the best 
 way of answering these questions. 
 
 Experiment 5. *The Direction of Sunrise and Sun- 
 set by Shadows. 
 
 Apparatus: Hatpin, protractor. 
 
 a. Stick a hatpin into the North-South line which 
 you determined in Experiment 1, or in Experiment 3. 
 Mark its shadow at sunrise and at sunset. Place the 
 straight side of the protractor along the North-South 
 line, with its center mark at the hatpin, and tell how 
 many degrees the direction of sunrise is from the North- 
 South line. Repeat for the direction of sunset. The 
 direction of sunset is as much away from the south direc- 
 tion as is the direction of sunrise. See if this is the same 
 after a few days. If this is true we can learn the di- 
 rection of sunrise by knowing the direction of sunset. 
 
 This experiment can be performed only at home. 
 
THE DIRECTION OF SUNRISE 
 
 11 
 
 The position of the sun varies from day to day, the 
 sun being farther to the south in winter than in sum- 
 mer. The sun rises in the east and sets in the west on 
 two days only. What are those days? How can you 
 find out? 
 
 Experiment 6. *To Record the Direction of Sunset. 
 
 a. Use the apparatus of Experiment 5. and arrange 
 your results in the form of a table. Direction should al- 
 ways be measured from the North-South line whenever 
 we wish to be exact. If the direction is just east or just 
 west, we say so. All other directions are given as the 
 number of degrees they are from the north toward the 
 east or west, and from the south toward the east or west. 
 If the direction of sunset is 80 degrees from the north, 
 the record should be: N. 80 W. If it is 70 degrees from 
 the south, the record should be: S. 70 W. What is the 
 difference between N. 90 W. and S.90 W? 
 
 b. The table for the record should be as follows : 
 
 Date 
 
 
 
 
 
 Direction 
 
 
 
 
 
 Once a week is often enough to take the observations. 
 Try it at home and see how your results compare with 
 those of the other pupils. 
 
 Review Questions- 3. 
 
 1. Begin with the direction north, and name the 
 four principal directions, and the half-way directions, 
 all the way around the circle, starring toward the east 
 Now repeat starting toward the west. 
 
 2. Where did the sun rise this morning? 
 
 * This experiment can be performed only at home. 
 
12 THE SUN, STARS, AND PLANKTS 
 
 3. How can you tell the direction of sunrise by 
 knowing the direction of sunset? 
 
 4. On what days does the sun rise at six o'clock 
 and set at six o'clock? 
 
 5. How can you tell when it is noon by a shadow? 
 
 6. How can you tell where the north is by a shadow? 
 
 7. If the sun sets S. 85 W. where does it rise? 
 Make a drawing of this, using the protractor, and obtain 
 your answer from the drawing. 
 
 8. If the sun sets N. 80 W. where does it rise? 
 Make a drawing as in the previous question. 
 
 7. Telling Time by the Sun. 
 
 In olden times, before clocks were made, people 
 used to tell time by the sun. Even now there are many 
 persons who can judge the time very nearly, by the posi- 
 tion of the sun in the sky. Yet it is impossible to learn 
 the time from the sun, with exactness, unless we make 
 use of a simple piece of apparatus. Just a stick driven 
 into the ground is all that is necessary. When the 
 shadow points north it is noon. See Experiment 3. 
 When the shadows cast at sunrise and sunset are oppo- 
 site each other the time of each is six o'clock. If the 
 semi-circle on the north side of the stick is divided into 
 twelve equal parts, the shadow will take one hour to pass 
 over each part. These divisions may be marked with 
 the hours between six in the morning and six at night. 
 Over how many degrees does the shadow move in one 
 hour? 
 
 Experiment 7. The Sundial. 
 Apparatus: Board, protractor, nail. 
 
TELLING TIME BY THE SUN 13 
 
 a. Draw a circle on a board using the protractor, 
 and divide it into 24 equal 
 parts. How many de- 
 grees are there in each 
 part? Drive a nail into 
 its center so that it makes 
 an angle of 90 with the 
 board, in all directions. 
 You can do this by hold- 
 i n g your protractor 
 against the nail as you 
 drive it. Draw a line from 
 the nail lengthwise of the board and place the board so 
 that this line runs north and south. How can you do this? 
 Mark this line 12, where it crosses the circle on the 
 north side, and then mark the other divisions properly 
 Is there any need to mark all of the divisions? Why? 
 What time does the shadow tell in the illustration? 
 
 8. Other Ways of Telling Time. 
 
 The sundial is a good way of telling time on sunny 
 days, but if we w r ant to know the time when the sun is 
 not shining we must use other methods. Long ago the 
 sand-glass, or hour-glass was invented to tell the length, 
 of an hour. This was made by connecting two bulbs or 
 globes by means of a small tube and having one glob^ 
 filled with sand. The filled globe was placed on top and 
 the sand slipped slowly through the small hole into the 
 lower globe. When all the sand had left the upper globe 
 an hour had passed. Then the hour-glass was turned up- 
 side down and a record was kept of the number of hours. 
 Why was the name hour-glass given? 
 
14 
 
 THE SUN, STARS, AND PLANETS 
 
 An ingenious scheme of telling time was by means 
 of water. Water was placed in a tank and allowed to 
 flow out through a small hole into a little tank where 
 there was a float made of wood. As the water rose the 
 float rose and indicated the hours by marks on the side 
 of the little tank. Nowadays clocks are used in which 
 wheels are allowed to turn slowly by means of a pen- 
 dulum. See Section 64. Next year we shall study more 
 about clocks. 
 
 Experiment 8. The Sand-glass. 
 Apparatus: Two small bottles, two stop- 
 pers, a piece of glass tubing y%" diameter, 
 small triangular file, fine sand. 
 
 a. Bore a hole in the two stoppers for 
 the glass tube and insert the tube in the 
 stoppers with their tops together. The tube 
 should not extend beyond the stoppers. Fill 
 one bottle with fine, dry sand, insert the 
 stoppers into the bottles and the sand-glass 
 is finished. 
 
 b. How long does it take for the sand to 
 run through? Keep changing the amount 
 of sand until it takes exactly one minute, or 
 exactly two minutes for the sand to run 
 through. Is this an hour-glass? A sand- 
 glass made like this and which would run 
 for three and a half or four minutes would 
 be useful for timing the boiling of eggs. 
 
THE HEIGHT OF THE SUN AT NOON 15 
 
 9. The Height of the Sun at Noon. 
 
 When is the sun highest in the sky? If the sun is 
 in line with the surface of the earth at sunrise, and grad- 
 ually becomes higher then gradually becomes lower un- 
 til at sunset it is again in line with the surface of the 
 earth, the highest point must have been reached half- 
 way between sunrise and sunset. What time is this? 
 What can you say about the length of shadows at sunrise 
 and at noon? At sunset and at noon? When is the 
 shortest shadow? Is the length of a shadow at noon al- 
 ways the same? If you do not know, how are you going 
 to find out? The varying length of a shadow shows the 
 height of the sun. 
 
 Experiment 9. The Height of the Sun at Noon by 
 Means of a Shadow. 
 
 a. Measure the length of the shadow of a window- 
 sill where the sunlight falls upon the floor at noon. 
 
 b. One week later measure it again. Is it the 
 same? Continue to measure the shadow once a week, 
 keeping a record of the lengths similar to the record 
 used in Experiment 6. Later you will have some ques- 
 tions about this experiment to answer. See Section 69. 
 
 We can measure the height of trees and buildings 
 and mountains in feet and inches but we cannot measure 
 the height of the sun in this manner. We always meas- 
 ure the height of the sun and stars by the number of de- 
 grees which we have to look upward from the surface of 
 the ocean or a lake. We call looking along the surface of 
 
16 
 
 THE SUN, STARS, AND PLANETS 
 
 Experiment 10. The Height of the Sun at Noon 
 Measured in Degrees. 
 
 Apparatus: Chalk box, protractor, nail, two tacks, 
 a body of water zero degrees high. We call directly 
 overhead ninety degrees high. 
 
 a. Take an empty chalk box and with the open side 
 toward you tack the protractor so that its straight side 
 crosses the short end of the box half-way and is parallel 
 with the long side. Drive a brad at the center point of the 
 protractor. With your rule held against the brad and 
 over the 85 division, mark the edge of the box with pen- 
 cil. Repeat for each 5. The marks on the edge of the 
 chalk box are not the same distance apart, but a shadow 
 of the nail falls on each mark in succession for each 5. 
 See if this is not true. The apparatus should appear like 
 the illustration. 
 
 b. Place the box so that the shadow of the nail at 
 noon falls. across the protractor and on the edge of the 
 
THE HEIGHT OF THE SUN IN DEGREES 17 
 
 box. What is the number of degrees that the sun is high 
 at noon? Repeat once a week and keep a record as in the 
 last experiment. Do you think that the sun is ever over- 
 head? Can you find out? 
 
 Review Questions, 4. 
 
 1. Xame four ways of telling time. 
 
 2. When did the sun set last night? Then when 
 did the sun rise yesterday? 
 
 3. If the hole in the tube of the hour-glass were 
 smaller would it make any difference in the time which 
 it would take for the sand to run through? 
 
 4. When is the sun the highest in the sky? How 
 can you tell ? 
 
 5. What are the two ways of stating how high the 
 sun is? 
 
 Next year yon will learn more concerning the sun, 
 stars, and planets. Now we are going to study about 
 what we receive from the sun. 
 
 Elem. Sci 2 
 
THE GUIDE 
 
LIGHT 
 
 10. The Light We Receive from the Sun. 
 
 Just after sunrise and just before sunset we may look 
 at the sun without hurting our eyes. The sun looks 
 large and red. The reason it looks large is because we 
 can compare its size with the size of other objects, and 
 when we notice that it appears larger than a distant house 
 or tree we realize that it is very large. The sun appears 
 red because the light in coming along the surface of the 
 earth has passed through a large amount of dust and fine 
 drops of water, which have sifted the light until most of 
 its strength has been taken out. 
 
 As the sun mounts higher and higher in the sky, the 
 light passes throueh less and less of the fine particles, 
 and we say the light becomes brighter. On hazy days, 
 or when there is smoke in the air, the sun looks red even 
 at noontime. To show that the reason why the sun ap- 
 pears red is because the light is sifted, we can perform 
 the following experiment. 
 
 Experiment 11. The Appearance of the Sun through 
 Smoked Glass. 
 
 Apparatus: Glass, candle. 
 
 a. Hold a piece of ordinary window glass in the 
 flame of a candle or the flame of a kerosene lamp, moving 
 the glass around in order to distribute the smoke. Tf 
 the glass is held still in the flame it will break. Smoke 
 one side only. The material on the glass is soot. 
 
 b. Hold the smoked glass between the sun and one 
 of your eyes, closing the other one. How does the sun 
 appear? Move the glass so that you look through more 
 
20 
 
 LIGHT 
 
 or less soot. How does the color of the sun appear to 
 
 change? 
 
 11. The Sunlight Makes Plants Green. 
 
 If a board or plank is laid on the grass for several 
 days, so that the sunlight cannot reach it, the grass will 
 be light yellow, and even white, when the board is first 
 removed. In a few days, however, the grass will regain 
 its usual green color. What caused the change? Pota- 
 toes and onions which sprout in the dark have very light 
 green or light yellow stalks and leaves. If these arc 
 brought into the sunlight they become green. Although 
 plants may grow in the dim light they need the sunlight 
 in order to grow well and to bear fruit. 
 
 Experiment 12. The Effect of Sunlight upon Grow- 
 ing Plants. 
 
 a. Cut a thin slice of cork from a stopper and trim 
 
 it into some shape, such 
 as a heart, or a cross, or 
 a clover leaf, and pin it 
 upon a growing leaf 
 which must be left upon 
 the tree. The best way 
 to fasten the piece upon 
 the leaf is to push two 
 pins through it, through 
 the leaf, and into another 
 piece of cork, which is 
 held on the under side of 
 the leaf. Do not touch it 
 for one week. At the end 
 
EFFECT OF SUNLIGHT ON PLANTS 21 
 
 of a week remove the pieces of cork and report how the 
 leaf appears. Let the leaf remain upon the tree and ex- 
 amine it at the end of another week. What has happened? 
 b. Try other designs and remove the leaves from 
 the tree when the cork covers are removed. See who can 
 make the best design. 
 
 Review Questions, 5. 
 
 1. Which way does the Great Dipper move around 
 the North Star, clock-wise or the other way around? 
 
 2. Look at the Great Dipper as early as you can see 
 it and as late as you can stay up, and see if you can tell 
 how many degrees it moves in one hour. 
 
 3. If the sun rises exactly in the east and sets ex- 
 actly in the west, through how many degrees does it 
 move? How many hours does it take? 
 
 4. At what hour does the sun rise when it rises ex- 
 actly in the east? Through how many degrees does the 
 sun move in one hour? 
 
 5. Why does the sun appear larger at sunrise and 
 sunset than it does at noontime? 
 
 6. Why does the sun appear red at sunrise and 
 sunset? 
 
 7. Is it ever red at any other time? Why? 
 
 8. What makes plants green? How can you sho.v 
 this? ' 
 
 9. When do plants grow best \Vliv? 
 
 10. Did you obtain your answers to t'lese qvicstinn ; 
 from books? What is the best way of ob fining these 
 answers? 
 
22 LIGHT 
 
 12. Other Changes of Color which are Caused by the 
 
 Sunlight. 
 
 If we are out in the sunlight a great deal our skin 
 becomes brown and we say that we are tanned. This 
 change of color is due to the sun and it takes place in 
 order to protect the body from the effects of too much 
 sunlight. Some persons do net t'Mi very easily, but be- 
 come red and often blisters are caused where the skin has 
 been exposed very long to the sunshine. Even persons 
 who do tan easily are sunburned if they try to become 
 tanned in a few days, while if they are not too long in 
 the sunlight at one time, the skin will protect itself by 
 putting a shield between the sun and the tender inner 
 skin. Just as smoked glass shut out so much sunlight 
 that we could look at the bright 'noonday sun without 
 hurting our eyes, so the tanned skin keeps out the strong 
 sunlight and we can expose it to the sun's glare without 
 harm. If the coloring material is not distributed evenly 
 throughout the skin little patches come which are called 
 freckles. 
 
 When we speak of the sun as causing plants to be 
 green and the skin to tan, we must remember that the 
 plants and the skin are alive. If the sun shines upon 
 things which are without life it can affect the color which 
 the things have, causing it to become lighter, and in some 
 cases, even making the material white or nearly white. 
 The change in color is called fading, while the removal of 
 the color from an object is called bleaching. 
 
 Experiment 13: Fading and Bleaching. 
 
 a. Obtain several pieces of differently-colored cot- 
 ton cloth and cut each piece into halves. Keep one of 
 
FADING AND BLEACHING 23 
 
 the halves of each piece in the dark, so that the color will 
 hot change. Wet the other halves with water and ex- 
 pose them to the bright sunlight until there is a change 
 in color. The pieces should be kept wet and it may take 
 a few days before there is much change. Make a list of 
 the colors and tell how soon they changed and what each 
 color became. 
 
 b. Wet and expose a piece of unbleached white cot- 
 ton cloth to the bright sunlight. Compare the result 
 with another piece which has not been exposed. 
 
 This is the old-fashioned way of bleaching and is the 
 best method, although it is slow. Bleaching may be ac- 
 complished much more quickly by the use of chemicals, 
 but the cloth is weakened and wears out more quickly. 
 
 The sunlight changes the color of certain chemicals 
 in a strange way. We can make use of this knowledge 
 and cause the sun to print designs for us on paper. The 
 simplest paper for this purpose is called blue-print paper. 
 It may be purchased cheaply or may be made very cheap- 
 ly. See Section 70. 
 
 Experiment 14. Blue Prints of Leaves and other 
 Articles. 
 
 Apparatus : Piece of window glass, leaves, lace, any 
 thin article, blue-print paper at least 4"x5". 
 
 a. Lay a piece of blue-print paper face up upon a 
 
24 
 
 LIGHT 
 
 book. Place upon 
 this a leaf, a piece of 
 lace, or any thin ar- 
 ticle, and cover with 
 the piece of glass. 
 Expose to the bright 
 sunlight until the 
 color of the paper is 
 a bronze. This color 
 must be learned by 
 experience. When 
 you think that the 
 color is right, re- 
 move the paper and 
 wash it for five min- 
 utes in running wa- 
 ter, or move it about 
 in a basin of water. The exposed part of the paper should 
 be a dark blue, while the rest should be a pure white. If 
 the blue color is not dark, it means that you did not leave 
 the paper in the sunlight long enough. If the. light 
 part is not white, but is somewhat blue, it is because you 
 exposed the paper too long. You should repeat this ex- 
 periment at home until you can obtain clear white prints 
 iiDon a dark blue surface. 
 
 Blue-print paper will also be used in Experiments 
 
 68 and 75. 
 
 Review Questions, 6. 
 
 1. If the sun should rise exactly in the south-east, 
 tell exactly where it would set. Why? 
 
SUNLIGHT GOOD FOR PLANTS AND ANIMALS 25 
 
 2. If the sun rises at six o'clock where do shadows 
 point at that time? Can you devise some method of 
 telling the exact east? Can you do this by means of the 
 sunset? 
 
 3. Is the sun ever exactly overhead? If it should 
 be exactly overhead what would the length of shadows 
 be then? 
 
 4. What is the best way of measuring the height 
 of the sun ? 
 
 5. How could you make a yellow figure upon a red 
 apple? 
 
 6. What does the sun do to your skin? Why does 
 this happen? 
 
 7. What does the sunlight do to color? 
 
 13. The Sunlight Good for Plants and Animals. 
 
 Although plants cannot move about the same as 
 animals, they do turn their leaves toward the sun and 
 even grow in the direction of the sunlight. Look at the 
 plants which are near the window in the room, and notice 
 how they lean toward the sunlight. This shows that the 
 sunlight is good for plants. If there were no sunlight 
 most of the plants would soon die. 
 
 The sunlight is also good for animals and man. If 
 a person stays indoors too much he will become sickly. 
 We should be out in the sunlight as much as possible, 
 and our buildings and houses should have many win- 
 dows so that the sunlight can enter freely. The sun has 
 a stimulating effect upon the body, and often persons 
 take sunbaths to improve their general health. Taking 
 a sunbath usually means sitting in the sunshine, but in 
 hospitals they are given by having the patients lie on 
 cots, being covered only by a sheet. 
 
26 LIGHT 
 
 There is another way in which sunlight helps us and 
 that is by killing disease germs. Much of our sickness 
 is caused by little plants, called bacteria, which are so 
 small that they cannot be seen. These plants grow best 
 in dark and damp places and for that reason we should 
 live in dry and sunny houses. If the sunlight which 
 comes in through many windows is too much for our 
 comfort we can shut it out, but if the windows are too 
 few in number there is no way of obtaining enough sun- 
 light. Windows are as cheap as the wall they take the 
 place of, and to have few windows is no economy. 
 
 14. Light Travels in Straight Lines. 
 
 What is meant by a straight line? When we say 
 "As straight as a string," do we mean a tightly pulled 
 string or a loose string? If carpenters wish to mark a 
 straight line on a building they rub some chalk upon a 
 string, stretch it tightly where they desire the line, and 
 then pulling the middle out a little, let it snap back upon 
 the wall. Some of the chalk leaves the string and makes 
 a straight line. Why is the line straight? Try making 
 straight lines with a chalk-line. 
 
 Now that you know just what is meant by the word 
 "straight" you can see that light travels in straight lines 
 If there is a candle or a lamp in a room, can you go any- 
 where in the room so that you cannot see the light? How 
 does the light come to you from the candle or lamp, 
 straight or curved? 
 
 Experiment 15. The Way Light Travels. 
 Apparatus: Slim stick three or four feet long, 
 string, two pieces of cardboard, candle. 
 
THE PINHOLE CAMERA 27 
 
 a. Make a bow of the stick by means of the string, 
 having the string come over the ends of the stick. Sight 
 
 along the tight string at a candle. Does the light come 
 to your eye in a straight line? 
 
 b. Make a hole with your pencil point through the 
 center of one piece of cardboard, and hold it three or four 
 inches from the lighted candle. Hold the other piece 
 of cardboard near the first piece, on the side away from 
 the candle. What do you see? A darkened room is 
 best for this experiment. If you do not see anything 
 distinctly it may be because the hole is either too large 
 or too small. What you see is an image. Explain whv 
 the image has the position in which you see it? If light 
 started from the top of the candle and passed through 
 the hole, in a straight line, would it strike the top or the 
 bottom of the second piece of cardboard? 
 
 Experiment 16. How to Make and Use a Pin-hole 
 Camera. 
 
 Materials: Chalk box, piece of ground glass to fit 
 as cover to chalk box, tinfoil, cardboard box, waxed or 
 greased paper to cover one end of cardboard box. 
 
 a. Cut a hole in the center of the bottom of the 
 chalk box about one-quarter of an inch across. Cover 
 this hole with a piece of tinfoil and make a pin-hole in 
 it. Slide the ground glass into the chalk box as a cover. 
 with the ground side out. The camera is finished. 
 
 b. Second method. Break one end out of a card- 
 board box, paste the cover on, and cover the open end 
 
28 
 
 LIGHT 
 
 with waxed paper, or paper with grease on it. Make a 
 hole with a pencil point in the end of the box which is 
 opposite the paper. Both cameras may be used in the 
 same way, but the first one will give better images. 
 
 c. Turn the pin-hole end of your camera toward 
 the objects you wish to see in the camera. Bright ob- 
 jects are the best for this purpose. Cover the head and 
 the other end of the box with a cloth, or a jacket, and you 
 will see an image in all its natural colors. Where is the 
 top of the image? Where is the right side of the image? 
 How do you explain this result? 
 
 Review Questions, 7. 
 
 1. If you look along the surface of a body of water 
 and then look exactly overhead, through how many de- 
 grees have you tipped your head? 
 
 2. If plants die, will the sun make the leaves green? 
 What besides the sunlight is necessary in order that the 
 plants be green? 
 
 3. What is the use of tan upon the skin? 
 
 What is the harm of using chemicals to bleach 
 
 4. 
 cloth? 
 
 5. 
 them ? 
 
 How do plants show that sunlight is good for 
 
THE REFLECTION OF LIGHT 29 
 
 6. If you were choosing a house in which to live, 
 what would you notice especially? 
 
 7. Give two proofs that light travels in straight 
 lines. 
 
 8. Why is the image in the pin-hole camera upside 
 down ? 
 
 15. The Reflection of Light. 
 
 Light travels in straight lines until it strikes against 
 something. Then it is turned back, and, although it still 
 travels in straight lines, the direction of the light has 
 been changed. This turning, or bending, of light is called 
 reflection. When the object which causes the reflec- 
 tion is smooth and shiny we seem to see the light in the 
 object. If you look at the reflection of any object in a 
 mirror, it seems to be back of the mirror. This is called 
 regular reflection, because what we see appears just like 
 the object. The appearance of an object in a mirror is 
 called an image.' Can you imagine why it is called an 
 image? 
 
 Experiment 17. Reflection from Mirrors. 
 
 Apparatus: Mirror at least 2"x4", block of wood 
 2"x2"x4", two rubber bands, foot rule, pin. 
 
 a. Turn the mirror toward the sun but tip it down- 
 ward so that the reflected light is on the wall about as 
 high as your head. Now turn the mirror about 45 de- 
 grees to the right. Through how many degrees does the 
 spot of light move? Repeat, turning the mirror to the 
 left. What result do you obtain? In turning the mirror 
 from the right position to the left position you moved it 
 
30 
 
 LIGHT 
 
 through 90 degrees. Through how many degrees did 
 the spot of light move? Make a drawing to show how 
 the light came from the sun and was reflected from the 
 mirror. 
 
 b. Fasten the mirror to the block of wood by means 
 of the rubber bands, and place it on a board. Stick a 
 
 pin two inches in front of the mirror and place the rule 
 so that its end touches the mirror and the pin comes at 
 the two inch mark. Look in the mirror and tell how far 
 back of the mirror the image of the pin is. Place the pin 
 at different distances and repeat. Having made several 
 trials, and having obtained the same results in each trial, 
 you can now draw your conclusions. How far back of 
 the mirror is the image compared with the distance the 
 object is in front of the mirror? 
 
DIFFUSED REFLECTION OF LIGHT 31 
 
 If the object upon which the light falls is rough some 
 of the light is reflected, but, since the rough surface is 
 made of tiny surfaces which face in all directions, the light 
 is scattered in all directions. In the case of this experi- 
 ment we cannot see the sun in the object if it is shining 
 upon it, but we see that the object is brighter. We call 
 this scattering of light, diffused reflection. All objects 
 which give light are seen by the light which they pro- 
 duce; all other objects are seen by the light which they 
 reflect. Light is diffused by particles of dust and tiny 
 drops of water in the air which are too small to be seen. 
 The light which we receive from the sky and from clouds 
 is due to diffused reflection. Diffused light is best for 
 the eyes. 
 
 Experiment 18. Diffused Reflection of Light. 
 Apparatus: Two blackboard erasers, glass. 
 Materials: Little milk, sheet of white paper. 
 
 a. Darken the room except for one window through 
 which the sunshine is coming. Notice the particles of 
 dust which are shining by reflected light. Stand across 
 the room and look for the particles in the sunbeam. Can 
 you see them? Why? The sky is bright for the same 
 reason that the sunbeam appears to be bright. If there 
 were no dust in the air you could not see a sunbeam. 
 Knock two blackboard erasers together in the sunbeam 
 and tell what happens. Look at your companions' faces 
 as you do this and see if they become brighter. 
 
 b. Put a glass of water in the sunbeam and notice 
 how it appears. Now add a drop or two of milk. What 
 color does the water become? Could you see a glass of 
 water across the room better if there were a few drops 
 
32 LIGHT 
 
 of milk in it? Why? Add some more milk and tell 
 what color the water becomes. When only a little light 
 is reflected what color is reflected? Why is the sky bine? 
 If all the light is reflected what color is it? 
 
 c. Notice the amount of light upon the ceiling. Xow 
 hold a sheet of white paper in the sunbeam and tell what 
 change there is in the amount of light. The moon shines 
 by light reflected from the sun, so moonlight is only sun- 
 light which has gone to the moon before coming to us. 
 
 Review Questions, 8. 
 
 1. Face the north. After turning 135 to the right, 
 in what direction are you facing? If you had turned to 
 the left, in what direction would you be facing? 
 
 2. If the sun is in the south direction every day in 
 the year, at noon, how can the sun be farther south in 
 winter than in summer? 
 
 3. If the sun sets at quarter before seven o'clock, 
 at vvhat time will it rise next day? 
 
 4. What is the best manner of finding the line which 
 is half-way between the shadows in Experiment 3? 
 
 5. What is the cause of freckles? Why do not all 
 persons become freckled? 
 
 6. If you looked at a very large and very bright 
 mirror would you see the mirror? Explain. 
 
 7. How do you see other persons? Do they give 
 light? 
 
 8. If you are five feet in front of a mirror and then 
 move three feet nearer, how much nearer are you to your 
 image? 
 
 9. Why are shades used over lamps and other 
 
 lights? 
 
SOURCES OF LIGHT 33 
 
 10. Why is the sky blue? You have seen the sky 
 when it is nearly white; what might cause a clear black 
 sky? 
 
 16. Light from Sources Other Than the Sun. 
 
 The sun is by far the best source of light. There 
 is no light so powerful, and none so beneficial to plants 
 and animals. Most animals, except those that prowl at 
 night, go to sleep soon after sunset; but man has long 
 been accustomed to staying awake much later. The need 
 of light was first met by the use of campfires. If a per- 
 son wished to leave the campfire he would remove a burn- 
 ing stick or fire-brand, and carry it with him. Thus the 
 torch was a natural outgrowth from the campfire. Later, 
 man learned that some kinds of wood, or wood which had 
 been soaked in grease, made better torches than a fire- 
 brand taken from the campfire. Still later, man made 
 lamps in which wicks burned in grease or oil. The flame 
 was uncovered and was smoky and dim. The candle was 
 a much more modern invention and, as you know, is still 
 used. The modern oil lamp, having the flame covered 
 with a chimney was a vast improvement over the ancient 
 oil or grease lamp. The burning of illuminating gas was 
 the next advance in lighting and was soon followed by the 
 electric light. 
 
 In all of the methods of producing light, except by 
 electricity, we obtain more heat than light in all cases 
 where light is obtained from burning a material. Even 
 the electric light produces more heat than light. 
 
 Experiment 19. Ordinary Sources of Light. 
 
 Apparatus: Oil lamp, Bunsen burner, gasoline 
 
 Elem. Sci 3 
 
 v 
 
34 
 
 LIGHT 
 
 lamp, or alcohol lamp, test tubes, test-tube holder. 
 
 Materials : Pieces of wood, candle, iron wire No. 28, 
 soft coal. 
 
 a. Darken the room as much as possible. Burn 
 pieces of wood (matches will do) and describe the light 
 which is obtained. Light the candle. Is the light steady? 
 Why? Light the kerosene lamp but do not put on the 
 chimney. Describe the flame and light obtained. Would 
 you like to be in a room for a long time with this kind of 
 a light? Put the chimney on and state what difference 
 you note. 
 
 b. If there is gas in the school, light 
 a Bunsen burner and describe the 
 light when the dampers at the bottom 
 are closed. Open the dampers. What 
 is the difference in the light? Hold 
 a piece of No. 28 iron wire, coiled into 
 a spiral, in the flame. Whe^ does the 
 light come from? Light the alcohol 
 lamp. What kind of light does burn- 
 ing alcohol give? Could you read by it. Hold the iron 
 
 Cut supplied through United State Department of Agriculture. 
 
COLD LIGHT 
 
 35 
 
 spiral in the flame. Could you read by this 
 light? This kind of light is called secondary, 
 because it is caused by the heat of the flame, 
 although the flame gives very little light. First 
 the heat comes from the flame, and secondly 
 the light comes from the wire. 
 
 c. Put a few pieces of wood, or soft coal, in 
 a test tube and hold it, by means of the test- 
 tube holder, in the alcohol or gas flame. Tell 
 what happens. See if you can light what is 
 coming out of the tube. It is gas. A large 
 amount of gas is made by heating coal. 
 
 While the heat from our sources of light is very 
 acceptable during cold weather, it becomes decidedly un- 
 pleasant on the hot nights when we must use lights. 
 For this reason scientists are trying to obtain some 
 source of light which will produce less heat than any we 
 now. use. 
 
 The whiter the light the less heat is produced com- 
 pared with the intensity of the light. Thus reddish or 
 yellowish lights produce much more heat than light, 
 while white light, although it produces a large amount 
 of heat, yields more light in proportion. Name some 
 yellow lights and some white lights. Nature supplies a 
 yellowish light which is practically cold. Fireflies and 
 glowworms are examples of this sort of light. Try to 
 catch some glowworms and examine them. Decaying 
 fishbones sometimes give a faint light, but, like the light 
 obtained from fireflies and glowworms, is of no practical 
 
36 LIGHT 
 
 value. This kind of light is called phosphorescence. So 
 far. man has not produced any really cold light which is 
 sufficiently strong for practical purposes. The experi- 
 ment shows one form of cold light which is used to a 
 slight extent on match-boxes, clock faces, and around 
 door bells so that they may be seen in the dark. 
 
 Experiment 20. Cold Light. 
 
 Apparatus: A matchbox with the word "matches" 
 made of luminous paint. 
 
 a. Place the matchbox so that the direct sunlight 
 will fall upon it for at least ten minutes, and then exam- 
 ine it in a dark room. It may be necessary to remain 
 in the dark room for a few minutes before your eyes 
 will become accustomed to the darkness. What do yon 
 see? 
 
 b. Keep the matchbox in a perfectly dark place for 
 two or three days and then examine it without removing 
 it from the dark. Can you see anything? 
 
 c. Place the matchbox in the sunlight for ten min- 
 utes and again examine in a dark room. What do you 
 conclude is the real source of light in the case of lumi- 
 nous paints? 
 
 Review Questions, 9. 
 
 1. Which side of trees has the most moss? Why? 
 
 2. How can you locate the south by means of a 
 watch? 
 
 3. If the sun rises exactly in the east, what is the 
 time of sunset? 
 
 4. Could you tell time by the Great Dipper? 
 
REVIEW QUESTIONS 37 
 
 5. What are some of the advantages of sunlight? 
 
 6. What are the two kinds of reflection, and what 
 is the chief difference between them? 
 
 7. If you move a mirror 10, how much will a re- 
 flected beam of sunlight move? 
 
 8. What are some of the sources of light? 
 
 9. Why does most light give heat? 
 10. Give examples of cold light 
 
THE QUIDS 
 
HEAT. 
 
 17. The Heat we Receive from the Sun. 
 
 The heat which we receive from the sun is necessary 
 for animal life and for plant life. As you know, it is 
 useless to plant seeds in very cold weather, and animals 
 often die when they do not have a warm place in which 
 to live. (Later we shall learn more about the effect of 
 heat upon plants.) 
 
 Just as the amount of light which we receive from 
 the sun varies with the different seasons, so the amouni 
 of heat which we also receive from the sun changes from 
 hour to hour and from season to season. When is the 
 warmest part of the day? When is the coolest part? 
 Look back at Section 10 and try to explain why this is 
 so. When is the warmest part of the year? When is 
 the coldest part? Perhaps you may obtain a suggestion 
 from Section 9. The next experiment will show why 
 the heat from the sun varies as it does. 
 
 Experiment 21. *The Varying Heat from the Sun. 
 
 Apparatus: Scissors, protractor. 
 
 Materials: Cardboard 12"x8", paper staple. 
 
 a. Make the apparatus as shown in the illustration. 
 The radius of the quarter circle should be five inches. 
 The divisions numbered 1 to 44 should be one-fourth 
 inch, and the movable strip should be one inch wide. One 
 inch of the end of the strip should be bent up and a quar- 
 * See Section 62 before performing this experiment. 
 
40 
 
 HEAT 
 
 ter inch hole made in the center. The line of divisions 
 represents the surface of a small part of the earth ; the 
 movable piece represents a sunbeam one inch wide. 
 
 When this "sunbeam" is perpendicu'ar to the "surface 
 of the earth" it covers one inch. How many degrees 
 are needed between two lines to make them perpendicular 
 to each other? If the "sunbeam" is at any other angle 
 it covers more than one inch of the "surface of the earth." 
 Now if you had just enough butter to cover one slice of 
 bread but had to cover two slices with it, how thick 
 would the butter be? Suppose that you were so un- 
 fortunate as to be obliged to cover three slices with the 
 same amount of butter, how thick would the butter be? 
 In a manner similar to this the sunshine is spread "thick 
 or thin" upon the surface of the earth, as the height of 
 the sun varies with the time of day and with the changes 
 of season. 
 
 b. Place your apparatus in the sunshine early in 
 the morning, or late in the afternoon, in such a manner 
 that the movable arm "sunbeam" may be aimed at the 
 
AMOUNT OF HEAT FROM THE SUN 41 
 
 sun, while the "surface of the earth" is parallel with the 
 real surface of the earth. The best way to do this is to 
 place the arm in such a position that the sun shines 
 through the hole in the bent end and falls lengthwise 
 along the middle of the strip. Read the angle on the 
 protractor. This is the elevation of the sun. Count the 
 number of spaces covered by the ''sunbeam." How 
 strong is the sunlight compared with what it would be 
 if it were perpendicular to the "surface of the earth?" 
 Remember your buttered bread! 
 
 c. Repeat (b.) at noon. What is the elevation of 
 the sun? How many spaces are covered by the "sun- 
 beam"? How strong is the sunlight compared with what 
 it was early in the day? 
 
 d. Take a reading once a week, of the sun at noon 
 and the number of spaces covered by the "sunbeam." 
 Continue this experiment the rest of the year. Keep a 
 record and compare it with the record which you are 
 keeping of Experiment 10 
 
 The amount of heat which is taken up by different 
 objects is very different, although all of the objects may 
 be near one another in the sunshine. Shiny objects do 
 not become very warm in the sunshine. What is the 
 effect of shiny objects upon light? They do the same 
 thing to heat and therefore they do not become warm. 
 White objects and those having light colors also are 
 quite cool in the sunshine, but are warmer than the 
 shiny objects because they do not reflect so much heat. 
 Dark colored and rough objects reflect very little heat 
 
42 HEAT 
 
 and thus become very warm. What color of clothing 
 should be worn in hot weather? Why? 
 
 Experiment 22. The Amount of Heat Received by 
 Different Colors. 
 
 Apparatus: Two spice cans of the same size, kero- 
 sene lamp, pieces of paper, white, red, yellow, and black. 
 
 a. Polish one spice can and smoke the other in the 
 flame of a kerosene lamp. Fill each with the same amount 
 of water and expose both in the bright sunshine. At 
 the end of twenty minutes dip a finger into each and tell 
 what the difference is between them. See Section 71. 
 
 b. While waiting for the water to become warm 
 expose the pieces of paper to the bright sunshine and 
 arrange them in the order of their warmth, putting the 
 hottest one first and the coldest one last. 
 
 We have seen that the amount of heat from sunshine 
 varies with the altitude of the sun, because when the sun 
 is low a given amount of sunshine is spread over a much 
 greater surface than when the sun is higher. Do you 
 think that if we could cause more sunshine to fall upon 
 a certain surface it would become warmer? See Experi- 
 ment 17. 
 
 There is another means by which light and heat 
 may be gathered together so that what falls upon a large 
 surface is caused to cover only a very small surface. 
 This is accomplished by the use of a circular shaped 
 piece of glass, thicker at the center than at the edges, 
 called a lens, or "burning glass." 
 
THE "BURNING GLASS" 43 
 
 Experiment 23. "The 
 Burning Glass." 
 
 Apparatus: A lens at 
 least 3" in diameter. 
 
 Materials : Bits of 
 paper, cloth, wood and 
 leather. 
 
 a. Hold the lens flat 
 to the light as it comes 
 from the sun and catch the light, after it has passed 
 through the lens, upon a piece of paper. Move the lens 
 toward or away from the paper until the spot of light is as 
 small as possible. Tell what happens. Why is it best to 
 have the spot of light as small as possible? Repeat, using 
 cloth, wood, and leather in the place of paper. Which 
 do you think would become hot quicker, black or white 
 paper? Try it. Notice the dark ring around the bright 
 spot. Where has the light gone? 
 
 Review Questions, 10. 
 
 1. What is the difference between fading and 
 bleaching? 
 
 2. What is a sunbath? How are they taken? 
 
 3. What is diffused light? How can it be produced? 
 
 4. Which is hotter, red light or white light? 
 
 5. Give some examples of cold light. 
 
 6. What part of the day is hottest? Why? 
 
 7. What material becomes the hottest in the sun- 
 shine? 
 
 8. How may we obtain a large amount of the sun's 
 heat in a very small space? 
 
44 HEAT 
 
 9. Write to pupils in schools four or five hundred 
 miles to the east or west of you, and ask them to tell you 
 the position of the Great Dipper at eight o'clock. . 
 
 18. Expansion Due to Heat. 
 
 Whenever anything- is heated it becomes larger. 
 This increase in size is called expansion. It is an in- 
 crease in length, breadth, and thickness. In liquids, 
 such as water, we notice the increase in volume. The 
 increase of volume is also evident in the case of gases, 
 of which air is an example. In solids, however, it is the 
 increase in length only, which causes us to be watchful. 
 
 The next time you are near a railroad track look 
 for the spaces between the ends of the rails. Are the 
 spaces large or small? Is the day hot or cold? If these 
 spaces were not left when the rails were laid in cold 
 weather, they would expand in hot weather and having 
 no space in which to expand, would bend sidewise, al- 
 lowing the car wheels to leave them. If you were lay- 
 ing rails on a very hot day would you put the ends close 
 together, or would you leave a space between them? 
 
 A practical use of expansion due to heat is made in 
 putting iron tires upon wheels. The tires are quite hot 
 when they are placed around the wheel and, as they cool 
 off they contract; that is, become smaller and thus grip 
 the wheel very tightly. See Section 72. 
 
 Experiment 24. Heat Causes Expansion. 
 
 Apparatus: Lamp chimney, candle, two small 
 blocks of wood, iron wire No. 18, rule, 4-ounce bottle, 
 cork to fit bottle, glass tube one foot long, tumbler, 
 alcohol lamp or Bunsen burner. 
 
HEAT CAUSES EXPANSION 
 
 45 
 
 a. Arrange appara- 
 tus as shown. Light the 
 candle and immediate- 
 ly mark the position of 
 the end of the wire. 
 Watch it and tell what 
 happens. What causes 
 the change? Blow out 
 the candle and explain 
 what happens. 
 
 b. Bore a hole in 
 the cork stopper so 
 that the glass tube will 
 fit it snugly. Push the 
 tube into the hole so 
 that the end is even 
 with the inner side of 
 
 the stopper, and insert the stopper tightly into 
 the bottle. Place the other end in a tumbler of 
 water. Warm the bottle with the hands, while 
 watching the end of the tube which is under 
 water. What happens? Why? Now warm 
 the bottle gently with a flame? What occurs? 
 Allow the bottle to cool. What do you see? 
 Why? As the air cooled it contracted thus 
 occupying less room, or space. The surface of 
 the water in the tube merely fits against the air. 
 
46 
 
 HEAT 
 
 c. Fill the bottle with cold water and in- 
 sert the stopper. The water should run up 
 the tube not more than two inches. Mark the 
 surface of the water with a piece of string tied 
 tightly around the tube. Heat the bottle 
 gently and tell what happens. Explain. Let 
 the water cool and explain what happens. 
 
 Some materials expand more than others 
 when they are heated. Thus tin expands 
 twice as much as does steel, while lead and zinc 
 expand still more. Steel expands the least 
 and zinc the most. This difference of expan- 
 sion leads to results which appear strange until 
 we think about what is occurring. A common example is 
 the loosening of preserve jar covers when the jars are 
 turned upside down and the covers placed in hot water. 
 The metal cover expands more than the glass does and 
 becomes loose. 
 
 Experiment 25. The Result of Unequal Expansion. 
 Apparatus: Apparatus as shown in cut, consisting 
 
 of a bar of brass and a bar of iron fastened together, 
 alcohol or gas lamp, bottle to hold apparatus. 
 
 Materials: Ice, salt. 
 
 a. Notice that the bars are straight. Heat very 
 hot by holding the bars in the flame. Which way do 
 thev bend, with the brass or the iron outside? Which 
 
UNEQUAL EXPANSION 
 
 expands the more, brass or iron? Let the bars cool and 
 see if they are straight, as at first. 
 
 b. Put the bars in salt and ice and let them become 
 cool. Which way do they bend? A metal which, when 
 heated, expands faster than another metal, also contracts 
 faster when cooled. The unequal expansion of metals 
 is made use of for practical purposes. The illustration 
 shows a strip of two metals which 
 pre joined together their entire 
 length, and then bent into the 
 shape of a shepherd's crook. As 
 the metals become warmer, due to 
 the increased warmth of a room, 
 the metal on the right expands 
 more than the other metal and 
 causes them both to bend to the 
 left. This bending brings together 
 the double metal and a screw 
 which act like an electric push 
 button. Instead of ringing a bell, 
 however, the electricity changes 
 the dampers of the furnace so 
 that the air of the room will not 
 be so warm. When the room 
 cools off, the metals bend the 
 other way and cause the electric- 
 ity to open the dampers again. 
 The machine is called a heat 
 regulator because it regulates 
 the amount of heat which a 
 room receives. 
 
 Cut supplied by the Jewell Heat Regulator Co. 
 
48 HEAT 
 
 Review Questions, 11. 
 
 1. What are the advantages of a sunny house? 
 
 2. How does heat come to us from the sun, in 
 curves or in straight lines? What makes you think so? 
 
 3. W r hy do you cover your head when you look at 
 the image in a pin-hole camera? 
 
 4. When you are reading at night should you have 
 the light shining directly into your eyes? How should 
 you light your books? 
 
 5. Can you really see a sunbeam ?What do you see? 
 
 6. What color of clothes should we wear in sum- 
 mer? Why? 
 
 7. What is expansion and what causes it? 
 
 8. Do all things expand the same amount? 
 
 19. The Thermometer an Application of Expansion. 
 
 Is it warm today? How do you judge? If you have 
 been running it may seem warmer to you than to some- 
 one who has been sitting quietly. The best way to learn 
 about the warmth is by means of a thermometer. This 
 is merely a tube with a large end called a bulb, and is 
 much like the bottle and tube which was used in Experi- 
 ment 24, c. In fact, we can use that apparatus in the 
 place of a thermometer, but the change in the height of 
 the water would be too little to measure easily for ordi- 
 nary changes of warmth. We saw, however, that as the 
 water became warmer it expanded and ran no the tube. 
 When anything is hot we say that it has a high temper- 
 ature, and when it is cold we call the temperature low. 
 Thus we can make this statement: When the temper- 
 
THE THERMOMETER 49 
 
 ature rose the water rose in the tube, and when the 
 temperature went down the water also went down. 
 Temperature then, is the condition of warmth, high 
 temperature being very warm and low temperature very 
 cold. 
 
 The usual thermometer is a very thin tube closed 
 at one end and with a bulb at the other end. This bulb 
 may contain mercury, sometimes called 
 quicksilver, or it may contain colored 
 alcohol. It is the mercury or alcohol in 
 the bull) which expands and pushes a tiny 
 thread of liquid up the tube. The ther- 
 mometer is marked either on the glass or 
 en the back, into divisions called degrees, 
 and these degrees are numbered from zero 
 up and down. There are two kinds of 
 markings on thermometers. The ther- 
 mometer which is used ordinarily is called 
 by the inventor's name, Fahrenheit, and 
 has the temperature of freezing water 
 marked 32 degrees, and the temperature of 
 boiling water marked 212 degrees. The 
 illustration shows a Fahrenheit thermom- 
 eter. The other thermometer is used by 
 scientists everywhere, and in many 
 foreign countries by everyone. This is 
 called the Centigrade thermometer and has 
 the freezing temperature of water marked 
 degrees and the boiling temperature of water marked 
 100 degrees. Of course the temperature of freezing 
 water is really just the same no matter what it is called, 
 just as you are the same person whether you are called by 
 
 Elem. Sci. 4 
 
50 HEAT 
 
 your real name or yonr nickname ; that is, 32 degrees 
 Fahrenheit and degrees Centigrade are the same tem- 
 perature. The temperature of boiling water is also the 
 same although it is called 212 degrees Fahrenheit and 100 
 degrees Centigrade. If you do not state whether the tem- 
 perature is according to the Fahrenheit thermometer or 
 the Centigrade thermometer, it is understood to be the 
 Fahrenheit. Degrees are marked the same as the degrees 
 of a circle, that is, in the place of writing 60 degrees Fah- 
 renheit we may put 60 F. 
 
 Experiment 26. How to Read a Thermometer. 
 Apparatus: Cheap thermometer. 
 
 a. Count the number of divisions between the fig- 
 ures 40 and 50. How manv spaces are there? What 
 is the difference between 40 and 50? Then how many 
 degrees does each space mark? All thermometers are 
 not marked the same and you should find out every 
 time vou use a thermometer just how many degrees are 
 covered by each space. 
 
 h. Obtain the temperature of the room. To do 
 this the thermometer should come to rest, that is, there 
 should be no difference between two readings taken two 
 or three minutes apart. The temperature of a room 
 should be 65 to 68 degrees Fahrenheit at the same height 
 as the heads of those sitting. If the temperature out- 
 doors is more than 68 degrees the temperature indoor* 
 may be uncomfortably high, but we should try to keep 
 the temperature at 68 degrees. 
 
 c. Take the outdoor temperature in the morning 
 just before school begins, at noon, and at the close of 
 
TEMPERATURE SENSATIONS 
 
 51 
 
 school. Keep a record of the temperature and you can 
 tell the hot days and the cold days, without trusting to 
 your memory. A record is to be trusted. See Section 
 69. 
 
 Another practical application of the unequal expan- 
 sion of metals is the dial thermometer. You have all 
 seen thermometers which have a hand moving over what 
 appears very much like the face of a clock. In the place 
 of the hours, however, the face is marked into divisions 
 which are numbered usually from zero to a hundred or 
 more. The word "Fah- 
 renheit" generally i s 
 printed upon the face of 
 the instrument. The 
 movement of the hand 
 is caused by the winding 
 up, or the unwinding, of 
 a spiral, due to the un- 
 equal expansion of the 
 two metals of which it is 
 composed. The illustra- 
 tion shows the spiral but 
 does not show the two 
 metals. Both metals are 
 quite thin and are fast- 
 ened together their entire length just as we learned the 
 heat regulator was made. 
 
 We should not depend upon our feelings in regard 
 to temperature. If we have been exercising we are warm 
 
 Cut supplied by the Standard Thermometer Co. 
 
52 HEAT 
 
 and may endanger our health by remaining in a room 
 which seems comfortable, when really it is too cold. 
 The thermometer is the only true guide to be followed 
 if we wish to know the real temperature. Of course, if 
 we are exercising, the temperature may be much below 
 68 degrees and do us no harm. The temperature of 68 
 degrees is proper for persons who are sitting still, or 
 moving about only a little. Is your room at the right 
 temperature? 
 
 The following experiment will show you haw little 
 it is possible to trust our feelings or sensations, 
 
 Experiment 27. Hot or Cold? 
 
 Apparatus: Three cups or other similar dishes, 
 sauce pan, alcohol or gas Tamp, ring stand r wire gauze. 
 
 Materials: Ice. 
 
 a. Fill one cup with water which is as hot as yoif 
 can bear putting your hand into; fill the 
 second cup with water at the temper- 
 ature of tfye room ; the third cup should 
 be filled with ice cold water. Place the 
 fingers of one hand in the hot water and 
 those of the other hand in the very cold 
 water and let them remain for one full 
 minute. Then place the fingers of both 
 hinds in the cup containing the water ar 
 the temperature of the room. How da 
 the fingers feel? Is the last water hot 
 or cold? Can you trust your sensations?" 
 
 Review Questions, 12. 
 
 1. If the sun rises at sven o'clock,, at what time 
 will it set? 
 
HEAT PRODUCES LIGHT 53 
 
 2. On which side of a street is it better to live, the 
 north side or the south side? Before answering think 
 where the sun is at noon and the direction front which 
 the sunshine comes. 
 
 3. What Is one thing we can do in order to keep 
 well ? 
 
 4. How may we obtain light from a flame which 
 gives a large amount of heat but gives, no light of itself? 
 
 5. If a person could be dressed in very shiny cloth- 
 ing, just like a mirror, would he be warm or cold in the 
 sunshine? Explain. 
 
 6. What use is made of the expansion of metals? 
 
 7. What use is made of the expansion of liquids? 
 
 8. How do you read a thermometer? 
 
 9. If the temperature in the morning is 48 F. and 
 at noon it is 65 F., what has been the change in temper- 
 ature? 
 
 10. Why should we not depend upon owr feelings 
 concerning the temperature of a room? 
 
 20. Heat Produces Light. 
 
 In Section 16 we learned that heat is one of the 
 sources of light and that it is impossible, as far as we 
 know at the present time, to produce cold light which is 
 strong enough for ordinary use. The light which we 
 obtain from heat, however, is not always the same, for 
 we have a dull red light, a yellow light and a dazzling 
 white light. What causes the difference? Did you ever 
 see a blacksmith working at his anvil? Sometimes the 
 iron is red-hot when he removes it from the forge, and 
 sometimes it is white-hot. Now you know the difference, 
 
 if you are near you can feel the difference. 
 
54 HEAT 
 
 We have learned that water boils at 212 Fahren- 
 heit, and we have always thought of "boiling hot" as being 
 very hot. Of course we have known that the fire is much 
 hotter but we have never thought much about it. Ice 
 water (32F.) is changed to boiling water (212F.) by an 
 increase of 180, yet the lowest temperature at which 
 there is a dull red light is about 950 Fahrenheit. The 
 temperature of bright red light is much higher, yellow 
 light is caused by a still higher temperature, while daz- 
 zling white light is caused by the extremely high tem- 
 perature of 2200 F. The electric light which we have in 
 our houses is a good example of light from heat. 
 
 21. Heat from Friction. 
 
 When two objects are rubbed together we say there 
 is friction between the objects. This friction makes it 
 hard for the objects to move past each other and it re- 
 quires more strength where there is much friction than 
 where the friction is less. Oil has the power to reduce 
 the friction between two objects and for that reason we 
 oil the bearings of machinery, also the curves of railroad 
 tracks, or we grease the places where we want one part 
 to slip easily over another part. Another name for 
 oiling is lubricating. 
 
 Try rubbing your hands together, pressing them 
 firmly against each other and moving them rapidly. How 
 do they feel? Why do persons rub their hands together 
 in cold weather? Rub a coin on your coat sleeve or on 
 the carpet and tell what happens. Feel of a gimlet after 
 boring a hole, and explain the results. Sometimes the 
 bearings of railroad car wheels become so hot, even if 
 
FIRE-MAKING 55 
 
 they are well lubricated, that they set the oil on fire, and 
 it is said there is a "hot box." 
 
 The old way of making fire depended upon friction. 
 So great heat can be produced by rapidly rubbing two 
 sticks together that they may be caused to glow, and even 
 burst into flame. Indians used this method for making 
 fire but it is hard to do, and requires skill and patience. 
 There is an easier way to accomplish the same result, 
 which we will now try. 
 
 Experiment 28. Primitive Fire-making. 
 
 Materials: Two blocks of wood 2"x4"x6", circular 
 wooden rod 7"long and pointed at both ends, a bow and 
 string, similar to the one used in Experiment 15, lubricat- 
 ing oil or grease. 
 
 a. Bore a hole part way through the blocks at their 
 center points, and arrange the apparatus as shown in the 
 illustration. Lubricate the hole in the top block but put 
 nothing in the hole in 
 the lower block. Why 
 is thh done? Bear down 
 hard on the top block 
 and move the bow back- 
 ward and forward very 
 rapidly. You may not 
 be able to make the lower block burn but you should be 
 able to make it smoke. Does the hole in the upper block 
 become equally hot? Why? This apparatus is called a 
 fire drill ; and this method of obtaining fire also was used 
 in olden times. 
 
 Another method of making fire was by means of the 
 flint and steel. Flint is a very hard stone and when it is 
 
56 
 
 HEAT 
 
 struck against iron or steel it removes little pieces, and 
 the friction is so great that they become almost white 
 hot. These tiny particles used to be caught upon shred- 
 ded linen, called tinder, which caught fire and burned. 
 As soon as the fire was obtained the tinder was covered 
 up and kept for next time. 
 
 Flint was also used for discharging guns. The 
 hammer of the gun carried a piece of flint, and as it fell, 
 it touched a piece of steel sending a shower of sparks 
 down into the powder. These guns were called flint- 
 locks. 
 
 Experiment 29. The Flint and Steel Gaslighter. 
 
 Apparatus: A friction gaslighter. 
 
 Materials: Alcohol, piece of cloth. 
 
 a. Examine the lighter, noticing the steel file and 
 
 Cut supplied by the Safety Gas Lighter Co. 
 
MATCHES 57 
 
 the material which rubs against it. This is not flint, bu* 
 the action of the lighter is very much like the old flint 
 and steel. 
 
 b. Make sparks with the lighter. To do so, quickly 
 rub the parts together. Feel of the sparks. Are they 
 hot? Make the sparks in illuminating gas. Does the 
 gas light? If there is no gas try lighting a piece of 
 cloth which is very wet with alcohol. Do gas and 
 alcohol have to be very warm in order to begin to burn? 
 
 The modern way of obtaining fire is by means of 
 matches. How do you light a match? What causes the 
 match to light? So the modern way is much like the 
 ancient way, after all. The only difference is that the 
 materials on the head of the match begin to burn at a 
 very low temperature, just as gas and alcohol were set 
 on fire by sparks which were not noticeably hot. As 
 soon as the match begins to burn its temperature rises 
 to more than 1000F. 
 
 Since matches are so easily set on fire, or ignited, as 
 it is called, they should be kept where there can be no 
 friction. It is not safe to keep them in the cardboard box 
 in which they are sold, for sometimes mice gnaw through 
 these boxes and ignite the matches by biting them. The 
 best way in which to keep matches is in a tin pail, 01 box, 
 having a tightly fitting cover. Not only is that the safest 
 way but the covered matches will also be kept dry and 
 good. 
 
58 HEAT 
 
 Review Questions, 13. 
 
 1. What is the color of the sun at sunrise and sun- 
 set? Why is it this color? 
 
 2. Which is hotter, red-hot or white-hot? 
 
 3. Why does the sun appear red when you look at 
 it through a piece of smoked glass? 
 
 4. In what direction do plants grow if they are 
 placed near a window? Why? 
 
 5. What is a straight line? How can you make a 
 straight line? 
 
 6. Why do we receive more heat from the sun in 
 summer than in winter? 
 
 7. What are the three sources of heat which we have 
 studied? 
 
 8. What would be the result if you did not lubricate 
 the hole in the upper block in Experiment 28? 
 
 9. What are the sparks when flint and steel are 
 struck together? 
 
 10. What is the difference between the modern way 
 of making fire and the olden way? 
 
 22. Heat from Combustion. 
 
 By far the greatest amount of the heat which we 
 enjoy comes from the sun. We have seen, however, that 
 as winter draws near we receive less and less heat from 
 the sun, so that it becomes necessary for us to obtain 
 heat from' some other source. Our usual source of heat 
 is from the burning of something. Combustion is 
 another name for burning. 
 
 There are two kinds of combustion, complete and 
 
HEAT FROM COMBUSTION 59 
 
 incomplete. By complete combustion is meant that all 
 of the material has been burned and none wasted. This 
 can be accomplished by giving the fire a proper amount 
 of air. Did you ever see heavy, black smoke coming out 
 a chimney? That smoke was part of the material which 
 should have been burned in the fire, and it meant a loss 
 to the one who was running the fire. The smoke showed 
 that there was incomplete combustion. If the com- 
 bustion had been complete there would have been no 
 visible smoke. 
 
 There are other reasons, besides economy, why fires 
 should not be allowed to send off vast amounts of smoke. 
 The particles of smoke, called soot, slowly settle and spoil 
 the appearance of buildings, soil our linen, and affect our 
 health. It is very bad for us to breathe in smoke and 
 soot. In many cities it is against the law to allow chim- 
 neys to smoke to any unnecessary amount. 
 
 Experiment 30. Complete and Incomplete Com- 
 bustion. 
 
 Apparatus: Alcohol lamp filled with alcohol, alcohol 
 lamp filled with turpentine, Bunsen burner. 
 
 Materials: Piece of broken chinaware, piece of iron 
 wire No. 28. 
 
 a. Light the alcohol lamp. Is there 
 any smoke? Is the flame hot? Hold a 
 piece of fine iron wire in the flame and 
 notice how hot it becomes. Hold a piece 
 of chinaware in the flame. Does any- 
 thing collect upon it? 
 
 b. Light the turpentine lamp. Is there any smoke? 
 
60 
 
 HEAT 
 
 Is the flame as hot as the flame of the alcohol? Why? 
 Which combustion is best? 
 
 c. Hold a piece of chinaware 
 in the flame of the turpentine 
 lamp. What collects upon it? 
 What is its color? 
 
 d. Hold the piece of china- 
 ware, with its coating, in the 
 flame of the alcohol lamp for sev- 
 eral minutes. What does this 
 prove about the wastefulness of 
 smoky combustion? 
 
 e. Light the Bunsen burner 
 and note the difference in the 
 flame when the air vents are 
 closed and when they are open. 
 When is combustion more nearly 
 perfect? 
 
 Alt 
 
 Ai? 
 
 23. Combustibles and Fuels. 
 
 Anything which burns is a combustible. Fuels are 
 only those combustibles which we ordinarily burn to 
 produce heat. You are familiar with the common fuels 
 which are coal, coke, wood, charcoal, oil and gas. What 
 do you notice when you burn them ? Do they all burn 
 with a flame? 
 
 In any combustion it is necessary to have air. In 
 our stoves the amount of air is regulated by dampers. Do 
 you open or close the dampers when you want a hot fire? 
 If there is not enough air the fire will smoke, and finally 
 go out. What causes incomplete combustion? 
 
COMBUSTIBLES 61 
 
 There is always a waste in the burning of fuels, even 
 when the combustion is complete, for all fuels, except oil 
 and gas, contain substances which do not burn. These 
 substances produce the ashes which we always find under 
 our fires. These ashes often contain particles of fuel 
 which would have burned if the fire had been hotter, so 
 it is seen that there are two losses from incomplete com- 
 bustion. What are they? 
 
 All combustibles, except some oils and some gases, 
 come directly from plants or animals. The following 
 experiment will show the difference between the two 
 kinds of combustion. 
 
 Experiment 31. The Combustion of Different Ma- 
 terials. 
 
 Apparatus: Alcohol lamp or Bunsen burner. 
 
 Materials: Wood, charcoal, coal, coke, paper, straw, 
 feathers, piece of wool, piece of silk, piece of cotton, piece 
 of linen, whalebone, piece of leather. 
 
 a. Hold a piece of each material in the flame and 
 note how it burns. Arrange all of those materials which 
 burn easily in one list and those that burn slowly in 
 another list. Which ones come from animals and which 
 from plants? Which is the safest clothing to wear when 
 near flames, cotton or woolen? 
 
 Goods may be prepared so that they will not burn 
 readily. This is called fireproofing. See Section 73. 
 
62 HEAT 
 
 24. Flames. 
 
 In our experiments with combustibles we found 
 that, while some of them burned with a flame, others only 
 glowed. The difference is caused by a gas, as only gases 
 burn with a flame. But, you will say, you saw wood 
 burn with a flame, and wood is not a gas. That is true, 
 but when the wood is heated so that it ignites, part of it 
 is changed into a gas and it is the burning of this gas 
 which causes the flame. It is just the same with a candle. 
 The wax, when it is heated, changes into a gas and the 
 burning gas causes the flame. Whenever you see a 
 flame you may be sure that a gas is burning. 
 
 There are two kinds of flames, those which give a 
 laro-e amount of light and those which give only a very 
 little light. Those flames which give light are called 
 luminous. Can you name some luminous flames? Name 
 one flame which is not luminous. How can you obtain 
 light from a flame which is not luminous? Luminous 
 flames show that the combustion is not complete, the 
 light being due to little particles which are not hot 
 enough to burn. A flame which can hardly be seen is 
 the result of very nearly complete combustion, and these 
 flames are much hotter than the luminous flames. 
 
 Experiment 32. The Cause of Flames. 
 
 Apparatus: Test tube, test-tube holder, alcohol 
 lamp, piece of glass tubing }/\" thick, 4" long. 
 
 Materials: Bits of wood, candle. 
 
 a. Put some bits of wood in a test tube and heat 
 them in the flame of an alcohol lamp. What do you see 
 
THE CAUSE OF FLAMES 63 
 
 collecting on the inside of the test tube? 
 Continue to heat the wood until smoke 
 comes out of the open end. Try lighting 
 this with a match. How does it burn, with 
 a flame or a glow? What must it be? 
 Where did it come from? 
 
 b. Continue to heat the bits of wood 
 until the smoke ceases to come off, then 
 remove from the flame. After the tube 
 has cooled a little pour out what remains 
 from the wood. What does it look like? 
 How does it burn? Why does it burn 
 this way? 
 
 c. Light a candle, let it burn for a short 
 . . ,, time, and then blow it out. Have a burning 
 \ '\ /7 match all ready to hold over the candle. It 
 
 should ignite. What burns? 
 
 d. Light a candle and hold a glass tube in 
 the flame as shown in the illustration. A 
 gas will pass up the tube and may be ignited 
 at the top. Where does the gas come from? 
 
 e. If there is gas, try the experiment as 
 shown in the illustration. 
 
 Review Questions, 14. 
 
 1. What is our guide from which we may learn 
 direction in the open country? How can you find the 
 guide? 
 
 2. What direction is 45 to the east of north? What 
 direction is S. 45 W?. 
 
64 HEAT 
 
 3. Can you see a light in the dark. Can you see a 
 person in the dark? Explain. 
 
 4. What kind of light is best for the eyes? 
 
 5. What are the sources of heat? 
 
 6. When you see smoke coming from a chimney in 
 large quantities what do you know about the fire which 
 causes it? 
 
 7. What is the difference between combustibles and 
 fuels? 
 
 8. Why do some things burn with a flame while 
 others only glow when they are burning? 
 
 9. What are the best combustibles, those from 
 plants or those from animals? 
 
 10. What makes a flame invisible? 
 
 25. First Aid to the Burned. 
 
 If the clothing is on fire the flames may be slapped 
 out, unless a large amount of the clothing is burning. Tn 
 this case the person should roll, or be rolled, upon the 
 floor. This crushes out the flames. Where possible the 
 person should be wrapped in any heavy material, such as 
 a mat or a rug, or even a coat. The wrapping should be 
 very tight. The person should not be allowed to stand, 
 as the flames will rush upward, setting more of the cloth- 
 ing on fire, and perhaps causing the person to breathe 
 the flame, which is very dangerous. Under no circum- 
 stance should the person be allowed to run about. If 
 persons would act quickly, harmful and even many a 
 dangerous burning accident could be avoided. Be quick ! 
 
 Experiment 33. Drill for Extinguishing Burning 
 Clothing. 
 
THE TREATMENT OF BURNS 65 
 
 Apparatus: Children. 
 
 Materials: Rug or coat. 
 
 a. Let one child be supposed to have burning cloth- 
 ing and let two or three other children slap out the imag- 
 inary flames, and wrap the burning child in a rug or 
 coat, and roll him upon the floor. 
 
 The pupils who do this should be those who are 'best 
 fitted to illustrate the method for the class. As other 
 pupils improve they should be allowed to show the class 
 this drill, perhaps at the end of each month. 
 
 The treatment of burns which are not severe is very 
 simple. Just moisten the burnt part with warm or cold 
 water and put on all the baking soda which will stick. If 
 the burn is quite bad, but has not blistered, the baking 
 soda may be bandaged on the burn with clean cloth which 
 has been torn into strips three-fourth of an inch wide. 
 
 If the burns are serious the water blisters should be 
 pricked with a needle, which has been heated ret-hot and 
 used as soon as cool, to allow the water to run out, and 
 then apply a mixture of equal parts limewater and olive 
 oil. Cover the burn with absorbent cotton which has 
 been soaked in the same mixture, and bandage snugly, 
 but not tightly. If the burns are very serious it is best 
 to call a physician. 
 
 Limewater may be prepared by putting one ounce of 
 fresh unslaked lime into a pint of cold water, shaking 
 until the lime breaks up, and allowing to settle. The 
 clear liquid should be poured off the top and kept in well- 
 stoppered bottles. A bottle containing equal parts of 
 
 Elem. Sci. 5 
 
66 HEAT 
 
 lime-water and olive oil should be kept in every kitchen. 
 If limewater is not at hand, use baking soda and olive oil. 
 
 Any of the following materials may be used for 
 burns: baking soda, olive oil, limewater, white lead and 
 linseed oil, powdered chalk, cornstarch, laundry starch, 
 flour of any kind, mucilage or dissolved gelatine covered 
 with any of the powders mentioned above. Since quick- 
 ness means much to the patient, ease in obtaining the 
 remedy should have first consideration. 
 
 There is another danger which is connected with 
 burns because the skin is usually destroyed. This gives 
 the bacteria a chance to enter and produce trouble for us. 
 To overcome these little plants we must bathe the 
 affected parts with some material which is an antiseptic, 
 that is, something which is against the poisoning. We 
 should do this whenever we break our skin by any means. 
 There are many antiseptic washes to be obtained in drug 
 stores and the proper kind can always be obtained. 
 
 Heat is harmful to bacteria if the temperature is 
 212 F. Where articles are known to contain bacteria 
 they may be killed by keeping them at the boiling point 
 of water for twenty minutes, or a shorter time at a higher 
 temnerature. 
 
 26. Conduction of Heat. 
 
 When we use a stove-poker for a few minutes, the 
 part which we are holding becomes uncomfortably hot. 
 We call this travelling of heat along an object, conduction. 
 Tf the heat reaches the cold end quickly, we say that the 
 material is a good conductor. 
 
 If we put a wooden handle on our poker, we may 
 
CONDUCTION OF HEAT 67 
 
 poke as long as we wish and our hands will not be burned. 
 That is because wood is a poor conductor. Most metals 
 are good conductors of heat, although some metals do 
 not conduct heat as well as others. Water is a poor con- 
 ductor of heat. 
 
 Experiment 34. Good and Poor Conductors of Heat. 
 
 Apparatus: Alcohol or gas lamp, pieces of copper 
 and iron wires No. 12, 6"long, test tube. 
 
 a. Hold the end of the copper wire in one hand and 
 the end of the iron wire in the other hand, and put the 
 free ends into the flame of a burner. Which one be- 
 came warm first? Which is the better conductor? Hold 
 the poor conductor in the flame and notice that it takes 
 a long time to become hot at the hand. 
 
 b. Fill the test tube nearly full of water and place 
 as shown in the flame of a burner, so that the top of the 
 water is heated. Do not let the flame touch the glass 
 where there is no water, as 
 
 it will break. When the 
 water boils at the top how 
 it the bottom? Is water a 
 food or a poor conductor oi 
 heat? If vou wanted tn 
 heat water where would you 
 heat it, at the bottom or 
 top? How does the ocean 
 become heated, at the top or 
 the bottom? 
 
68 HEAT 
 
 If a substance is a good conductor of heat and it is 
 colder than our bodies, it will take heat away from us if 
 we touch it, and we will say that the body is cold. Yet 
 there may be another substance which is just as cold as 
 the first one, but is a poor conductor of heat, and this one 
 will not conduct the heat away from us, and we may say 
 that it is warm. Thus we find that standing with bare 
 feet upon a rug is pleasanter than standing upon the bare 
 floor, or upon an oilcloth. The rug is not a conductor of 
 heat. It is called a non-conductor. Therefore our feet 
 remain warm. The oilcloth, or the bare floor, is a much 
 better conductor of heat and takes it away from our feet 
 and they feel cold. Linen, cotton, and silk feel cold 
 because they are good conductors, while woolen goods 
 and furs feel warm because they are poor conductors of 
 heat. Poor conductors make the warmest clothing. 
 
 If the substance is warmer than we are, and is a 
 jrood conductor, it feels warm because it readily gives 
 its heat to us. A non-conductor does not seern as warm, 
 although it may be. warmer, because it does not conduct 
 the heat to us. Here again we must not trust our sensa- 
 tions but must depend upon a thermometer, if we wish 
 to learn the real temperature of the substance. 
 
 It is not a good plan to stand upon, or sit upon, 
 materials which are good conductors, when they are 
 colder than we are, for they take our heat away and 
 make us cold. Stones are good conductors and many a 
 chill has been caused by sitting upon stone walls. 
 
 If heat is not desired it may be kept out by the use 
 of non - conductors. For this reason milk cans are 
 wrapped in jackets to keep out the heat of the sun on hot 
 days. 
 
REVIEW QUESTIONS 69 
 
 Review Questions, 15, 
 
 1. What makes the sun appear red and large at sun- 
 rise and sunset? Does the sun really change its color 
 and size? 
 
 2. What causes the sky to be light blue on some 
 days arid dark blue on other days? 
 
 3. When you pour hot water into a glass dish the 
 inside expands before the heat reaches the outside. What 
 happens? Is glass a good conductor of heat? Do you 
 think thin glass would break? 
 
 4. What is friction? How can you make friction 
 much less than it would be if you did nothing? 
 
 5. Why do we build a fire by first putting in paper, 
 then little pieces of wood, and finally large pieces of 
 wood, or perhaps coal? 
 
 6. What must be done if the clothing is on fire? 
 
 7. What is the most common remedy for burns? 
 
 8. Why do linen sheets feel cold when we first get 
 into bed? 
 
 9. How does the teakettle become warm when on 
 top of the stove? 
 
 10. Why do firemen wear woolen shirts? Give two 
 reasons. 
 
THE GUIDE 
 
AIR, 
 
 27. Air a Necessity of Life, 
 
 There can be no life of any sort without air. Ani- 
 mals breathe it and plants need it, in order to live. There 
 is air even in water and fishes could not live without 
 this air. We live in an ocean of air which surrounds the 
 whole earth and this ocean is called the atmosphere. The 
 meaning of the word "atmosphere" is breath-sphere. Do 
 you think that the atmosphere is well named? 
 
 Experiment 35. Holding the Breath and Deep 
 Breathing-. 
 
 a. See how many seconds you can hold your 
 breath. You should be able to hold it one minute, with 
 practice. 
 
 b. Stand erect with the chest up, without having 
 any of your muscles hard and take just as long a breath 
 as you can, breathing through the nose. When you 
 think that you cannot draw in, or inhale, any more air, 
 contract all the muscles of the body, and hold the breath 
 for a few seconds. Slowly let the air come out. Letting 
 the air out is called exhaling. Repeat several times and 
 then see how long you can hold your breath. Always 
 take this exercise before holding your breath. Why can 
 you hold it longer than you did at first? 
 
 Experiment 36. *The Effect of Depriving a Plant 
 of Air. 
 
 * Adapted from Farmers' Bulletin 409, U. S. Dept. of Agriculture. 
 
72 
 
 AIR 
 
 Apparatus: Two glasses or bottles, burner, stand, 
 dish for heating. 
 
 Materials: Geranium cuttings, olive oil, cardboard. 
 
 a. Heat the water slowly. What comes out of the 
 water long before it boils? Boil the water for two or 
 three minutes and allow it to cool. 
 
 b. Fill one of the glasses two-thirds full of water 
 which has not been boiled, and fill the other glass two- 
 third full of the boiled water, 
 after it has become cold. Pre- 
 pare two cardboard covers, as 
 shown in the illustration, and 
 put a geranium cutting in each. 
 Po*ir olive oil on the surface of 
 the boiled water to a depth of a 
 quarter of an inch, being careful 
 not to get the oil upon the cut 
 
 end of the geranium slip. Watch the cuttings for a week 
 or ten days and note the difference between the growth 
 of roots upon the two cuttings. Do plants need air in 
 order that their roots may grow? 
 
 28. Air in the Soil and in Water. 
 
 If we take a handful of soil and examine it we will 
 notice that it is made up of many fine particles of irregu- 
 lar shape and size, which do not fit tightly together. Thus 
 there are left a large number of tiny holes between the 
 little particles, which all added make a large space. These 
 spaces are all filled with air. 
 
 When the sun is shining upon the soil it becomes 
 warm and the air in it expands, and some of it comes out 
 of the soil. As the ground cools off at night, the air within 
 
 Cut supplied through United States Department of Agriculture. 
 
AIR IN SOIL AND WATER 
 
 73 
 
 the soil contracts again and more air enters to take the 
 place left by the contraction. Since plant roots need air, 
 can you see the advantage of cool nights during the sum- 
 mer? 
 
 Water also contains air, as was learned from the last 
 experiment. In the next experiment we will see just 
 how much air is held in water when it is cold. 
 
 Experiment 37. To Show the Presence of Air in 
 Soil and Water. 
 
 Apparatus: Tin can, glass, two test tubes, one-hole 
 stopper, glass tube two feet long, burner. 
 
 Materials: Soil, water. 
 
 a. Fill the tin can nearly full of dry soil, loosely 
 packed, and quickly pour a glassful of water upon it. 
 What do you notice? What can you say about the 
 presence of air in soil? 
 
 b. Throw away the wet soil and fill again with 
 loosely packed, dry soil. Fill the glass even 
 
 full of water and pour it slowly upon the soil, 
 not allowing the top of the soil to be covered 
 with water at any time. Continue to add 
 water until the soil will take no more and the 
 water surface comes up to the surface of the 
 soil. How much water have you added? 
 How much air was there in the soil? 
 
 c. Arrange the apparatus as shown in the 
 illustration. To bend glass tubing it should 
 be held in the flame of an ordinary gas 
 burner, or an alcohol lamp, or in the flame 
 produced by an attachment for the Bunsen 
 burner, as shown in the illustration, called a 
 
74 
 
 AIR 
 
 wing top burner. At least 
 two inches of the tube should 
 be heated, and it should be 
 turned slowly so that all sides 
 may receive the same amount 
 of heat. When the glass has 
 become soft, it should be re- 
 moved from the flame and quickly bent at right angles 
 and held in this position until it has hardened. If the 
 bend is not well rounded it shows that the glass was not 
 evenly heated. The second bend is to be made in the 
 same way. 
 
 Fill the test tube full of cold water and after properly 
 arranging the apparatus, gently heat it. The outlet tube 
 should dip into a little water. As the water is heated it 
 expands and passes over into the other test tube. Do 
 you see any air collecting in the heated tube? Where 
 does it come from? If the water is heated too much it 
 will begin to boil and may force most of itself over into 
 the other tube. It is not necessary to heat it until it 
 boils. Allow the water to cool and notice what part of 
 the tube is occupied by air. This is the air which fishes 
 use, and they could not live in water which had been 
 boiled and then cooled. 
 
 Review Questions, 16. 
 
 1. Which kind of soil will become the warmer in 
 the sunshine, dark colored or light colored? Which is 
 best for early planting? 
 
 2. When is the sunshine warmer, when the sun 
 appears red or when it appears white? 
 
 3. How many degrees away from the direction of 
 
THE COMPOSITION OF THE ATMOSPHERE 75 
 
 a shadow is the direction of the light? How do you 
 define these two directions? 
 
 4. How can you tell the time of sunrise if you 
 know the time of sunset? 
 
 5. What is the proper temperature for the school- 
 room and the home? 
 
 6. Why does the ground become warm faster than 
 a pond? 
 
 7. Which will burn us the more, a piece of wood 
 or a piece of copper, if both are at the same temper- 
 ature? Explain. 
 
 8. Where do we live in our ocean of air, at the bot- 
 tom or the top? Could we live anywhere else than where 
 we do? 
 
 9. Would it do any harm to water plants so much 
 that the ground would be covered with water? 
 
 10. What collects on the inside of a glass of cold 
 water if left in a warm room? 
 
 29. The Composition of the Atmosphere. 
 
 Some mornings when you come to school it is fogg> 
 and you think how damp the air is. Even if it is not 
 foggy you have often noticed that the air is damp and 
 you have heard persons say, "Clothes will not dry today." 
 On other days, however, it has been brisk and bracing 
 and the air has been called dry. Though the air has 
 seemed dry it still contained water in an invisible form. 
 It is from the invisible form of water that dew, fog, and 
 clouds are formed. 
 
 The amount of water in the air varies from day to 
 day and even from hour to hour. The air near large 
 bodies of water usually contains more moisture than 
 
76 
 
 AIR 
 
 does the air in other places. Why? If you leave a 
 glass of cold water in a warm room, what collects on the 
 outside? There is another part of the atmosphere called 
 carbon dioxide, which also varies according to the local- 
 ity. In the open country there is very little of this gas, 
 but in cities, and in rooms where there are a large num- 
 ber of persons, it may increase so as to harm us, for it 
 is not a good gas to breathe. 
 
 Although the amount of water and carbon dioxide 
 in the atmosphere varies greatly, the largest portion of 
 the air is composed of two gases which do not vary 
 About one-fifth of the air is oxygen, and about four- 
 fifths is nitrogen. These gases are so important that we 
 will study them one at a time. Thus you see that the air 
 which you thought was just one thing is really composed 
 chiefly of four substances: nitrogen, oxygen, carbon 
 dioxide, and water. Besides these, there are argon, dust, 
 and bacteria. 
 
 Experiment 38. The Amount of Oxygen in the Air. 
 Apparatus: Saucer, glass, candle, flat cork stopper. 
 
 a. Cut the can- 
 dle so that it is 
 not more than one 
 inch long and 
 make a "life pre- 
 server" for it from 
 the stopper. To do 
 this, cut a round 
 hole in the stop- 
 per, in which the 
 candle will fit 
 tightly. The cork 
 
CARBON DIOXIDE 77 
 
 need be only one-fourth of an inch thick, but it should be 
 placed near the wick end of the candle. Fill the saucer 
 with water, place the candle upon the water, light it, and 
 cover with the glass. Tell what happens. 
 
 b. How high did the water rise? The candle has 
 used all of the oxygen and left the nitrogen. How much 
 of the air is nitrogen and how much is oxygen, according 
 to your experiment? Why did not the candle go out at 
 once? Why did not the water begin to rise when the 
 candle was covered? Before answering this question 
 you must think of the effect of heat upon a gas. See 
 Experiment 24. Why did the water continue to rise 
 after the candle went out? 
 
 Note : The same experiment may be repeated with 
 a large bottle, having straight sides, and a cake pan, or 
 bread pan, to see if the same results will be ob- 
 tained. 
 The following experiment is for the teacher: 
 
 Experiment 39. The Amount of Carbon Diox- 
 ide in the Air. 
 
 Apparatus : A twenty-ounce glass-stoppered 
 bottle, glass measure graduated in cubic centi- 
 meters, medicine dropper graduated to hold one- 
 third of a cubic centimeter. 
 
 Materials: Limewater solution (pure water 
 left in contact with slaked lime until the water 
 will not take up any more lime. Dilute the clear 
 decanted liquid with 99 times its own volume), 
 phenolphthalein solution (dissolve one part ot 
 phenolphthalein in 500 times its own weight of 50 
 per cent alcohol.) 
 
78 AIR 
 
 a. Fill bottle with pure water, and empty it in the 
 place where the air is to be tested. This will insure the 
 bottle being filled entirely with the air of the room. Add 
 10 c. c. of limewater solution and one-third c. c. of 
 phenolphthalein solution, stopper, and shake. If the red 
 color disappears in three minutes or less, the air is unfit 
 to breathe. 
 
 30. Oxygen and its Uses. 
 
 We have learned that air is necessary for life of any 
 kind and that it is composed of nitrogen, oxygen, carbon 
 dioxide and water. We have also learned that it is the 
 oxygen which caused the candle to burn since it stopped 
 burning when all the oxygen had been used. Therefore 
 we call oxygen the supporter of combustion. Just as the 
 candle needs oxygen in order to burn, so we need oxygen 
 in order to live. It it only the oxygen of the air which 
 the body uses ; the nitrogen is exhaled unchanged. If 
 there are many persons in a close room most of the oxy- 
 gen will soon be used and the air will become unfit for 
 breathing. Headaches and drowziness are more often 
 produced by bad air than by hard lessons. Yawning is 
 caused, by a desire to obtain more oxygen. 
 
 Since it is the oxygen of the air which supports com- 
 bustion and air is composed of only one-fifth oxygen, we 
 might suspect that combustibles would burn much more 
 vigorously in oxygen than air. Let us see if this is true. 
 
 Experiment 40. To Prepare and Use Oxygen. 
 Apparatus: Test tube, test-tube holder, burner. 
 
THE PREPARATION OF OXYGEN 79 
 
 Materials: Potassium chlorate (powdered), manga- 
 nese dioxide, splinters of wood. 
 
 a. Mix equal parts of potassium chlorate and man- 
 ganese dioxide on a piece of paper, and pour into a test 
 tube. Hold the test tube in the flame of the burner, by 
 means of the test-tube holder, until it becomes very hot. 
 Then light a splinter of wood, let burn for a while, blow 
 out the flame, and insert the glowing end into the tube, 
 continuing to heat the tube. What happens? There is oxy- 
 gen coming from the mixture in the tube. Does wood 
 burn better in oxygen than in air? Is oxygen invisible or 
 visible? Colored or colorless? 
 
 Review Question, 17. 
 
 1. Why does the skin become tanned? 
 
 2. If you run toward your image in a mirror going 
 ten feet a second, how fast will you approach your image? 
 
 3. How should the lights of a house be arranged to 
 give the best light for the eyes? 
 
 4. Why are woolen underclothes better protection 
 from cold than cotton garments? 
 
 5. Should the thermometer hang near the floor, on 
 the level of your head, or near the ceiling of a room to be 
 of use to us? 
 
 6. How can you show that there is air in water? 
 
 7. Give all the reasons which make you think that 
 there is water in the air. 
 
 8. How can you show that about four-fifths of the 
 air is nitrogen? 
 
 9. Why does pure oxygen support combustion 
 better than air? 
 
 10. What is one cause of headaches? 
 
AIR 
 
 31. Nitrogen and its Uses. 
 
 As we have learned, about four-fifth of the air is 
 nitrogen. We saw that it was oxygen which supported 
 combustion and that pure oxygen supported combustion 
 much more vigorously than air, because air is only one- 
 fifth oxygen. What do you think the effect would be 
 upon fires if all of the air were oxygen? One of the uses 
 of nitrogen, then, is to lessen the effect of oxygen. Where 
 the amount of one substance is reduced by the addition 
 of another we say that the first substance is diluted, and 
 call the process dilution. Nitrogen dilutes the oxygen. 
 Pure oxygen is sometimes inhaled, under the advice of a 
 doctor, by those who have weak lungs. 
 
 For a long time it was thought that nitrogen hid no 
 other use than to dilute the oxygen. Now it is known 
 that tiny plants, so small that they are invisible, called 
 bacteria, live upon the roots of some of the larger plants 
 and absorb the nitrogen from the air. This they change 
 into material which is needed by the larger plants. This 
 
 Cut supplied through United States Department of Agriculture. 
 
CARBON DIOXIDE 81 
 
 is one example of the good which bacteria do for us. 
 Later we shall learn that they help us in many ways. 
 The larger plants cannot take in the nitrogen until it 
 has been changed by the bacteria, and many of the plants 
 could not live if it were not for the bacteria. 
 
 The little lumps upon the roots of the plant in the 
 illustration are called nodules. Each nodule is the 
 home of bacteria. The illustration is the root of the 
 garden-pea, but there are nodules upon the roots 
 of many other plants and trees. Whenever you see these 
 nodules you will know that there are many helpful 
 bacteria within them. 
 
 The kind of food which the plants form from the 
 material supplied by the bacteria is the source of our 
 strength. When we study plants and food we shall learn 
 more about these bacteria and their work. 
 32. Carbon Dioxide. 
 
 The amount of carbon dioxide in the air varies 
 according to the location. Near factories there is a larger 
 amount than in the open country, or on the ocean, while 
 in a room where there are many persons the amount may 
 become very great. This shows that fires produce it and 
 animals exhale it. In the open country, air contains 
 only three or four parts of carbon dioxide in ten thousand 
 parts. The gas is a combination of oxygen and carbon. 
 Coal, coke, and charcoal, all of which are fuels, are chiefly 
 carbon. If the air of the room contains eight to ten parts 
 of carbon dioxide in ten thousand parts of air it is unfit 
 for us to breathe. Since exhaled air contains four hun- 
 dred parts in ten thousand, it can easily be seen that there 
 should be, not only a supply of fresh air, but the stale air 
 should be removed continually. In addition to carbon 
 
 Elem. Sci. 6 
 
82 AIR 
 
 dioxide we exhale small, invisible particles of decayed 
 animal matter which also are poisonous unless diluted 
 with plenty of fresh air. You all know the story of the 
 Black Hole of Calcutta, and the fatal results from the lack 
 of fresh air. 
 
 Carbon dioxide has its use and it is a most important 
 one. Plants absorb it and break it up into its parts, car- 
 bon and oxygen. The plants keep the carbon, making- 
 wood of it, and give out the oxygen to the air again. 
 Thus plants purify the air. For that reason we should 
 have plants in our school rooms and houses. Plants owe 
 their ability to take in carbon dioxide to the green color- 
 ing matter in their leaves and stalks. We have learned 
 that the sunlight causes plants to be green, and so you 
 see that it is the sun which causes plants to grow. That 
 is why plants grow in the direction of the sun. 
 
 Experiment 41. Carbon Dioxide from Combustion 
 and from the Breath. 
 
 Apparatus: Candle, funnel, syringe bulb, glass tube, 
 10" long, test tube. 
 
 Materials: Limewater (all the slaked lime that will 
 dissolve in water ; use the clear liquid only.) 
 
 a. Arrange apparatus as shown in the illustration, 
 light candle, and force the gases which come from the 
 candle into the limewater. What happens? What 
 caused the change? 
 
 b. Blow out candle and repeat. In this case it is 
 the air of the room which is being forced into the lime- 
 water. Does the change take place? 
 
 c. Take the apparatus out of doors and repeat. Do 
 
SOURCES OF CARBON DIOXIDE 
 
 83 
 
 you finally see any change? 
 
 d. Now repeat (b.) and (c.), counting the number 
 of times it is necessary to squeeze the bulb in order to 
 obtain the same result. Divide the number of times it 
 takes indoors by the number of times required out of 
 doors. The result will show about how much more car- 
 bon dioxide there is indoors than out of doors. If the 
 room is properly ventilated there should be little differ- 
 ence. Is the schoolroom properly ventilated? 
 
84 
 
 AIR 
 
 e. Blow through the glass tube into some limewater. 
 Do you think that you exhale the same gas as a candle 
 produces? 
 
 The illustration shows a method of collecting the 
 oxygen which is given off by a plant. In this case it 
 must be a water plant, but oxygen is given off by all 
 green plants. If you wish to perform this experiment yon 
 must collect some water plants and place them in the 
 bottom of a large dish. Cover them with a funnel, 
 which must be of glass, and fill the dish until the top 
 of the funnel is covered with water to a depth of. one 
 inch. Take a test tube, fill it with water, cover the end 
 with your thumb, and invert it in the dish, not letting 
 
 any water escape. Slide the 
 test tube over the end of 
 the funnel and set the whole 
 apparatus in the bright sun- 
 shine. In a few minutes you 
 will see bubbles forming, 
 and in a day or two, the test 
 tube will contain enough 
 oxygen for a test. To remove 
 the test tube lift it from the 
 funnel, putting your thumb 
 again over its mouth, while 
 it is under the water, and re- 
 move from the water. Turn 
 the test tube right side up. 
 
RESPIRATION 85 
 
 keeping the thumb tightly in place. Test for oxygen. 
 How will you do it? Is it oxygen? How do you know? 
 
 33. Respiration. The Necessity for Pure Air. 
 
 Breathing consists of inhaling and exhaling. Breath- 
 ing is also called respiration. Do you know how many 
 breaths you take in a minute? How can you find out? 
 Do you always take the same number of breaths in a 
 minute? What makes you breathe faster sometimes? 
 Your heart beats faster when you breathe faster. A 
 grown person, or adult, breathes 18 times a minute, not 
 exercising, and his heart beats 72 times a minute, or four 
 times the number of breaths. Young persons breathe 
 faster and their hearts beat faster. Usually the heart 
 beats four times for each breath. 
 
 We should breathe through our nose because it is a 
 sort of sieve which keeps the dust from passing on to the 
 lungs, and it also warms the air a little before it reaches 
 our lungs. If persons find trouble in breathing through 
 the nose they should consult a doctor. 
 
 The amount of air which we ordinarily inhale and 
 exhale at each breath is 30 cubic inches. When we draw 
 a long breath, or "heave a sigh," the quantity of air 
 which we inhale or exhale is about 130 cubic inches. By 
 trying, we can exhale about 100 cubic inches more. Even 
 then there remains about 100 cubic inches which cannot 
 be exhaled. The amount of air which the lungs hold is 
 called their capacity. All persons do not have the same 
 lung capacity, but where the capacity is less than it 
 should be, it may be increased by breathing exercises and 
 the right kind of physical exercise. 
 
86 AIR 
 
 Experiment 42. The Capacity of the Lungs. 
 
 Apparatus: Large bottle, holding at least a gallon, 
 cork stopper to fit, large pan, holding at least two gallons, 
 piece of rubber tubing three feet long, piece of glass 
 tubing which has had its rough edges rounded off in a 
 flame. 
 
 a. Fill the bottle full of water, insert the stopper 
 and invert in a pan in which there is about two quarts of 
 water. Remove the stopper and slip one end of the 
 rubber tubing up into the bottle, which should be tipped 
 a little to one side, and held there, in order not to jam the 
 tubing. The glass tubing should be inserted in the other 
 end of the rubber tubing to serve for a mouthpiece, which 
 may be washed before each pupil uses it. Take several 
 long breaths before measuring your lung capacity. Then 
 take the longest breath possible, place the tube in the 
 mouth, and blow hard. Keep on blowing until you can- 
 not exhale a bubble more. Immediately remove the 
 rubber tube from the bottle and estimate your lung 
 capacity. There are 231 cubic inches in a gallon. If 
 100 cubic inches of air still remained in your lungs, what 
 is the capacity of your lungs? 
 
 The amount of air which is needed per minute, in a 
 room in which there are several persons, cannot be found 
 out by multiplying the number of cubic inches used in 
 each breath by the number of breaths per minute, and 
 by the number of persons in the room. We must remem- 
 ber that the air which we exhale contains four hundred 
 parts of carbon dioxide in ten thousand, while the proper 
 
THE NECESSITY FOR TURE AIR 87 
 
 amount of carbon dioxide is no more than eight or ten 
 parts in ten thousand. Now 400 is 50 times 8. This 
 means that one breath spoils 50 times that amount of air, 
 not only for others but even for ourselves. For this 
 reason it is very necssary to have a large supply of fresh 
 air. If there are lights burning in the room, such as 
 kerosene lamps or gas, much more air is needed. An 
 ordinary light spoils as much air as four persons in the 
 same time. Electric light does not affect the air. 
 
 Review Questions, 18. 
 
 1. Why does pouring hot water into a glass dish 
 break it? Would there be any difference if the glass 
 were thin? 
 
 2. What is the result of incomplete combustion? 
 Why is it not wise to allow incomplete combustion? 
 
 3. Why should a person not run if his clothing is on 
 fire? What should he do if he is alone? 
 
 4. What kind of clothing is most liable to burn? 
 
 5. What is the composition of the air? 
 
 6. What would happen if there were no nitrogen? 
 
 7. How does carbon dioxide get into the air? 
 
 8. At the ordinary rate of breathing, how much air 
 will twenty pupils breathe in half an hour? How much 
 air will they spoil in the same time? 
 
 9. Find the number of cubic inches of air in your 
 schoolroom and tell how many times it must be changed 
 in every half hour in order to give you enough fresh air, 
 if you were the only person in the room. 
 
 10. Solve Problem 9 for the number of persons in 
 Tour room. 
 
THE GUIDE 
 
WATER. 
 
 34. Water is a Liquid. 
 
 A block of wood, or a stone, has a shape which does 
 not change. What is the shape of a quart of water? 
 Water will fit any dish that you put it into, and thus has 
 no shape of its own. Anything which has a shape which 
 does not change is called a solid. If the material fits the 
 dish into which it is put and leaves no empty spaces, it 
 is a liquid. 
 
 While water is a liquid and fits perfectly every dish 
 into which it may be put, there is one part which is 
 always the same. This is the top of the water, called its 
 surface. The surface of water is always flat, or hori- 
 zontal. Another name for horizontal, is level. All 
 parts of a horizontal, or a level line are the same distance 
 from the center of the earth. If we want to make the 
 floor of a house level we can do so by means of a hori- 
 zontal surface of water. 
 
 Experiment 43. The Level. 
 
 Apparatus: Pie tin, small round bottle and stopple. 
 
 a. Half fill the pie tin with water and place it upon 
 the board which you are to make level. If the water 
 does not come up the same distance all around the tin, 
 when it is on the board, the board is not level, or hori- 
 zontal. Put little pieces of wood or stones, under the 
 low sides of the board until the water is at the same 
 height all around the tin. Can a board be horizontal in 
 one direction, say north and south, and not horizontal in 
 
90 WATER 
 
 the east and west directions? Is there any difference 
 between being level and being horizontal? 
 
 b. Half fill the little bottle with water and lay it 
 upon its side on a board. When the surface of the water 
 is the same distance up from the side of the bottle, all 
 along, the board is horizontal in the direction of the 
 length of the bottle. How can you make a board level by 
 
 means of the bottle? 
 The bottle is called a 
 level. A simple level 
 is shown in the illustra- 
 tion. In this level the 
 tube is curved so that the air bubble is always at the 
 highest part. 
 
 A block of wood, or a stone, will stay where you put 
 it; water will run off. All liquids act in the same manner 
 and are said to flow. If the water faucet is gradually 
 shut so that the Pow of water becomes less and less, the 
 stream will suddenly break into drops. How would a 
 rainstorm be if water did not break into drops? Water- 
 drops are all the same size unless the drops come together. 
 Do raindrops ever come together? 
 
 On account of the flowing of water there is a saying, 
 "Water always seeks its own level." This means that 
 the surface of water is at the same level everywhere if 
 the water can flow freely between all parts. 
 
 Experiment 44. *Water Seeks its own Level. Size 
 of Drops. 
 
 * It is desirable to take Sec. 58 before performing this experiment. 
 
WATER SEEKS ITS OWN LEVEL 
 
 91 
 
 Apparatus: Funnel, rubber tubing, glass tube to 
 make apparatus as shown in the illustration, medicine 
 dropper, graduate (50 c. c.), small dish. 
 
 Fill the funnel and tube with water and hold the 
 
 a. 
 
 funnel and tube in various positions. What do you 
 notice in regard to the level of the water in the funnel 
 and the level of the water in the tube? 
 
 b. Fill the medicine dropper and carefully count 
 the drops which are needed to make 5 cubic centimeters. 
 In reading the graduate it must be placed on a level table 
 and the reading must be taken with the eye on a level 
 with the surface of the water. Read the lower surface 
 of the water. How many drops in one cubic centimeter? 
 If there are 946 cubic centimeters in a quart, how many 
 drops of water are there in a quart? 
 
 35. Water can Pass into Some Things. 
 
 If we put a sponge into water some of the water 
 goes into the sponge. The same thing is true of clothing. 
 
92 WATER 
 
 We know that if we step into water it soaks into and 
 through our shoes. All bodies which allow water to pass 
 into them or through them are called porous, on account 
 of many little holes in them which are called pores. 
 When porous bodies take in water we say that they 
 absorb water. There are other bodies which are porous 
 although they do not seem to be so unless we experiment 
 with them. A brick is very porous, and so are many 
 rocks. As you know, the ground is porous, or the rain 
 would not sink into it. 
 
 Experiment 45. *Porous Bodies Absorb Water. 
 Apparatus: Balance, weights, cake pan. 
 Materials: Sponge, cloth, brick, porous stone. 
 
 a. Weigh the sponge dry, let it soak in water and 
 weigh again. What is the gain in weight? How much 
 water could a pound of sponge take in? 
 
 b. Repeat with the brick. The brick should remain 
 in the water for a full day. 
 
 c. Repeat with the cloth and porous stone. 
 
 The only reason that some bodies are porous is 
 because they contain little holes, or pores. If we wish 
 to keep the water out of a body we must close the holes, 
 just as we close the gate to keep out the dogs or other 
 animals. Preparing material so that it will not permit 
 water to enter is called waterproofing. See Section 74. 
 
 Experiment 46. To Make Porous Bodies Water- 
 proof. 
 
 * Section 59 should precede this experiment. 
 
WATERPROOFING 93 
 
 Apparatus: Burner, ring stand, wire gauze, tin 
 dish. 
 
 Materials: Piece of cloth, 4"x5", paraffin. 
 
 a. Melt the paraffin by gentle heat and dip the 
 cloth into it. While the paraffin on the cloth is still 
 warm, shape the cloth into a four-sided box. When cold 
 it should hold water. What keeps the water from going 
 through the cloth? 
 
 Rubber is the material which is commonly used to 
 fill the pores of porous material, in order to make it 
 waterproof, as rubber is not altered by ordinary changes 
 in temperature. Do you think that your box would 
 hold hot water? 
 
 While it is not pleasant to have water come through 
 our clothing or even our houses, the porosity of materials 
 has its use. Water which passes through the small pores 
 has lost a large amount of its dirt. The separation of 
 dirt from water, by means of porous bodies, is called 
 filtration, and the porous body is called a filter. All 
 water which comes from the earth in springs and wells 
 has been filtered by passing through the porous ground. 
 We can filter water, where necessary, by means of porous 
 dishes or porous paper. 
 
 Experiment 47. Filtration. 
 
 Apparatus: Funnel, funnel-holder (cut a hole in the 
 small end of a chalk box), test tubes. 
 
94 WATER 
 
 Materials: Sawdust, sand, filter paper. 
 
 a. To use filter paper, fold it 
 in halves and then again in quar- 
 ters, as shown in the illustration. 
 Separate one thickness from the 
 other three and place in funnel. 
 Mix some sawdust, sand and 
 water. Then filter. Does the 
 water pass through clear? 
 
 Review Questions, 19. 
 
 1. What are two causes of the variation in the heat 
 which we receive from the sun? 
 
 2. What causes contraction? 
 
 3. What part of the room is the warmest, near the 
 ceiling, on the level of your head, or near the floor? 
 
 4. What are the advantages of deep breathing? 
 How can you prove your answer by figures? 
 
 5. Name the parts of the air that are used by plants, 
 stating how they are used, and the parts of the air which 
 are taken in by animals, giving the use of each part. 
 
 6. If you were given a long rubber tube, which 
 would reach across the room, and two glass tubes to fit 
 the ends of the rubber tube, tell how you could put two 
 shelves on the opposite sides of the room at exactly the 
 same level. 
 
 7. How could you find out whether a body is porous? 
 
 8. Name all of the porous bodies you can think of 
 and state the advantages or disadvantages which are due 
 to their porosity. 
 
 . 9. What is meant by waterproofing. Give some 
 examples of waterproofing. 
 
SOLUTION 
 
 95 
 
 10. Why is water from springs usually clear, while 
 water in rivers is dirty? 
 
 36. Solution. 
 
 When we put sand or sawdust into water we could 
 still see it. Can you see sugar when you have put a little 
 into water and have stirred it well? If a solid disappears, 
 when put into a liquid, we say that the solid dissolves, 
 and we call the result a solution. Not only does water 
 dissolve solids but it can also hold gases in solution. 
 Any liquid which can dissolve solids or gases is called a 
 solvent. In Section 28 we saw that water can hold con- 
 siderable air in solution if the water were cold. The best 
 way to learn more about solution is by experimenting. 
 
 Experiment 48. Solution and its .Oddities. 
 
 Apparatus: Two glasses, tin spoon, burner, tin 
 cans, thermometer, funnel, filter paper, glass rod. 
 
 Materials : Sugar, salt, baking soda, cream of tar- 
 tar, ammonium chloride (commonly called sal ammoniac). 
 
 a Fill a glass full of water. Very slowly add 
 some sugar while carefully stir- 
 ring. Note that it is possible to 
 add considerable sugar without 
 making the water overflow. Now 
 add some salt in the same way 
 to the same water. Can you do 
 it without making the water 
 overflow? What is one of the 
 oddities of solution? Try filter- 
 ing the solution. Do the sugar 
 and the salt pass through? The 
 method of pouring liquids from a 
 glass is shown in the illustration. 
 
96 WATER 
 
 b. Put a little cold water in one glass and the same 
 amount of hot water in another glass. Now see how 
 much sugar will dissolve in the cold water and how much 
 in the hot water. When a solvent holds all of a solid it 
 can, the solution is said to be saturated for that temper- 
 ature. Which solution becomes saturated first, the hot 
 one or the cold one? Which is better for dissolving 
 solids, cold water or hot water? 
 
 c. Fill a glass one-fourth full of cold water, take its 
 temperature, and then add half as much sal ammoniac ^ 
 there is water. Stir rapidly and immediately take its 
 temperature. What is another oddity of solution? Can 
 you explain (b.) above, now that you have done (c.) ? 
 Do you think that the solution is saturated? Why? 
 
 d. Put a little dry baking soda and a little dry 
 cream of tartar into a dry glass. Nothing will happen. 
 Now add some water. What happens? Solution per- 
 mits the action of one material upon the other. The 
 gas is carbon dioxide and it is this gas which makes 
 soda biscuits rise- 
 
 Water owes its power of removing dirt to the fact 
 that it can dissolve so many substances, but there are 
 many kinds of material which water cannot dissolve. 
 Fortunately for us there are other solvents which can 
 dissolve some of these. Two common examples of spe- 
 cial solvents are alcohol and gasolene. We should be 
 very careful when we are using either of these solvents. 
 
OTHER SOLVENTS 97 
 
 not to be near a fire, or even be in the same room with a 
 fire or a burning lamp,, for both are very easily set on fire. 
 Gasolene produces a gas which may be set on fire by a 
 flame although several feet away. 
 
 Experiment 49. *The Use of Gasolene and Alcohol 
 as Solvents. 
 
 Apparatus: Two small bottles with stoppers. 
 
 Materials: Gasolene, alcohol, kerosene, pieces of 
 cloth, grease (lard), rosin,- pitch. 
 
 a. Shake a little grease with water in a bottle. Does 
 the grease dissolve in the water? Pour off the water, add 
 gasolene and shake again. What is the result? 
 
 b. Put a very little grease on a piece of cloth. This 
 will make a grease spot. To remove the grease spot the 
 space all around the spot should be wet with gasolene 
 before putting the gasolene upon the spot itself. If 
 gasolene is put upon the grease first the grease will 
 spread and leave a ring after the spot has been removed. 
 Try putting the gasolene upon a grease spot on a second 
 piece of cloth and notice the familiar ring when the 
 gasolene has evaporated. 
 
 c. Shake ? Httle powdered rosin witb water in a bot- 
 tle. Does the water dissolve the rosin? Pour off the water, 
 add some alcohol, and shake again. What is the effect of 
 alcohol upon the rosin? Pour the result upon a smooth 
 piece of wood and allow the alcohol to evaporate undis- 
 turbed. How does the wood appear? Rosin is used in 
 cheap varnishes. Do the cheap varnishes scratch easily? 
 
 d. Put some pitch upon a piece of cloth and remove 
 
 * This experiment may be omitted or performed only by 
 the teacher. 
 
 Elem. Sci. 7 
 
98 WATER 
 
 it with kerosene. It may be necessary to allow the cloth 
 to soak in the kerosene for some. time. Pitch may be 
 removed from the hands with kerosene. The kerosene 
 may then be removed with soap and water. 
 
 37. Crystals. 
 
 We have seen that some solids can disappear in 
 solution. Do you think that they can come out of solu- 
 tion and appear again? The only way in which we can get 
 a solid out of solution is to drive off the water by means 
 of heat, called boiling, or we can let the water pass off 
 slowly and without bubbling. This last method is called 
 evaporation. Let us learn about this by some experi- 
 ments. 
 
 Experiment 50. Crystallization. 
 
 Apparatus: Burner, ring stand, wire gauze, two 
 beakers, three glasses, stirring rod, deep dish. 
 
 Materials: Alum (powdered), copper sulphate, 
 common salt, string. 
 
 a. To a little water add one half as much powdered 
 alum and stir for a few minutes. Does it all dissolve? 
 Now put it on the ring stand, resting it upon the wire 
 gauze, and heat it until it boils. Does heat aid solution? 
 Place the beaker containing the solution, in a dish of cold 
 water and stir it constantly until cold. What happens? 
 Heat the beaker again until all of the alum has dis- 
 solved and then place it again in the dish of cold water, 
 but do not stir it or touch it until it is cold. What is 
 the result? What you see are crystals. Which method 
 produces the larger crystals, rapid cooling or slow cool- 
 ing? Keep the crystals. 
 
CRYSTALLIZATION 
 
 99 
 
 b. Repeat (a.), using the same amount of water but 
 using three-fourth as much copper 
 
 sulphate as water, in the place of alum. 
 What are your results? Note the 
 shape of the crystals. Are they the 
 same as the alum crystals? A micro- 
 scope, such as is shown in the illu 
 tration will help you, although it is not a necessity. 
 
 c. Make a saturated solution of common salt, one 
 of alum, and one of copper sulphate. Place in separate 
 glasses and in each solution hang a piece of string from 
 a little stick placed across the top of the glasses. Set 
 aside for a few days. The water will evaporate and 
 leave the solids. Are all the crystals the same shape? 
 The crystals of any one substance are always the same 
 where they have formed slowly and have had plenty of 
 room in which to form. Can you tell the difference 
 between a salt crystal and an alum crystal? 
 
 There are many crystals in nature although there 
 are but six different kinds. We may imitate a few of the 
 crystals by cutting out the shapes, as shown in the illus- 
 
100 WATER 
 
 trations, from thick paper, folding on the dotted lines, 
 and pasting their edges together by means of strips of 
 paper. 
 
 38. Water for Drinking. 
 
 There is hardly any pure water as it occurs in nature. 
 On account of the great power which water has to dis- 
 solve so many substances, there is usually some material 
 held in solution. Fortunately for us, many of the sub- 
 stances found in water are not harmful to man, while 
 some of them are very helpful. The harmful substances 
 which are dissolved in water are usually so bad tasting 
 that there is little danger from them, for no one will drink 
 the water. 
 
 While the dissolved material is usually harmless, 
 there is great danger in drinking impure water. This is 
 due to a kind of plant life we have already become 
 acquainted with in Sections 13 and 25. Some of these, 
 which we learned were called bacteria, may cause typhoid 
 fever. Although the water is clear and seems pure, the 
 bacteria may be present. On the other hand, dirty 
 water may be free from bacteria and be harmless. Wells 
 should be so located that drainage cannot possibly reach 
 them, for decayed animal matter is what these bacteria 
 live upon. Since water can pass through the porous 
 rocks, wells must be far away from open drains and 
 stables. 
 
 The body requires a large amount of water and most 
 grown persons do not drink enough. The more water 
 we drink the better are the wastes carried from the body. 
 We have learned that while water can dissolve many 
 
DRINKING /" :*.OJ*(i*'-i l& } 
 
 things, a limited amount of water can dissolve only a 
 limited amount of any one solid. Thus, unless we drink 
 a sufficient amount of water, the impurities which are 
 produced in our bodies by the wear and tear of living, or 
 those which are taken in with food, will not be carried 
 off rapidly enough. Unless we are warm we should 
 drink all the water we desire. It is best to drink slowly 
 and often, rather than rapidly and in large quantities. 
 
 While the drinking of a large amount of water is 
 very desirable, and even necessary, yet there are other 
 common drinks which are harmful. Any drink which 
 contains alcohol, such as beer, wines, whiskey, brandy, 
 and many others, cannot fail to harm a person to some 
 extent. Alcohol is a poison, and even a small amount of 
 a poison will have some harmful effect. Some persons 
 who use drinks which contain alcohol may seem to be 
 unaffected, but they do not know how much greater 
 progress they might have made if they had left alcohol 
 alone. Alcohol should always be considered as a drug. 
 
 Compared with alcohol, coffee and tea are not very 
 harmful to grown persons unless used to excess. Young 
 persons should not drink either coffee or tea until they 
 have completed their growth. Even grown persons 
 should be careful not to drink too much of either coffee 
 or tea. A person who uses too much of these drinks 
 becomes nervous and irritable, and his eyes are often 
 affected. 
 
 Review Questions, 20. 
 
 1. Why is it warmer in summer than in winter? 
 Whv is it warmer near noon than at sunrise or sunset? 
 
V 52 , i JVH.J.P WATER 
 
 2. If your clothing should be set on fire, what 
 would you do. What would you do if you saw the 
 clothing of another person burning? 
 
 3. Why are you sure that there must be air in 
 water? 
 
 4. How much air does a person spoil by breathing 
 for one hour? 
 
 5. What is the best kind of light to use in our 
 houses? Why? 
 
 6. Why are brick houses sometimes damp? Could 
 the dampness have been prevented? 
 
 7. Why do we stir or beat frosting for cake for a 
 long time? If we did not beat fudge what would be the 
 result? 
 
 8. What is meant by evaporation? What causes 
 evaporation to be more rapid? 
 
 9. When do we need the more water for drinking, 
 when we have been perspiring a great deal, or hardly 
 perspiring at all? 
 
 10. Explain 'how harmful drinks may injure us 
 although we may not notice the effects. 
 
 39. Water for Cleansing. 
 
 The most important use for water is for drinking. 
 We shall see in the next section that plants, as well as 
 animals, require a large amount of water in order to live. 
 The use for water which is next in importance to its use 
 for drinking and for plants, is its use for cleansing. Water 
 owes its power of cleansing to its ability to dissolve so 
 many substances. 
 
 We know that if water has some dissolved substance 
 
HARD AND SOFT WATER 103 
 
 already in solution it will not dissolve other substances 
 as readily as will pure water. If water has very little 
 dissolved material in it, it will cleanse easily. We call 
 such water soft. Rain water which has fallen after it 
 has been raining for some time, is very soft. Why? 
 Water obtains its dissolved .material from the ground. 
 Water which contains dissolved substances is called 
 hard. Soft water makes suds with soap very easily 
 while hard water does not. Since soap has the power of 
 acting with the water to dissolve or loosen dirt, if it does 
 not dissolve in the water and form suds, the water is 
 hard to use for washing. Cleansing is much easier with 
 soft water than with hard water. 
 
 Experiment 51. *Hard and Soft Water. Soap. 
 
 Apparatus: Burner, ring stand, tin cup, pint bottle 
 with stopper. 
 
 Materials: Distilled water, powdered or shaved 
 soap. 
 
 a. Measure the smallest amount of soap which will 
 just begin to make suds when shaken with a half pint 
 of distilled water in a pint bottle. This will give you a 
 standard, for distilled water is absolutely pure and will 
 make suds with the least amount of soap. Any other 
 water will use more soap. 
 
 b. See how much soap is necessary to produce suds 
 with a half pint of ordinary water. Take another "half 
 pint of the same kind of water which has been boiled for 
 at least five minutes. Does it take more or less soap to 
 make suds with the boiled water than with the unboiled 
 water? Hard water which can be made soft by boiling 
 
 * See Experiment 79. Distillation. 
 
104 
 
 WATER 
 
 is called temporarily hard. If the water is not rendered 
 soft by boiling it is called permanently hard. Was the 
 water you used temporarily or permanently hard, or was 
 it soft? 
 
 Since hard water requires more soap than soft water, 
 in order to produce suds, the use of hard water for cleans- 
 ing is more expensive than the use 
 of soft water. Water which is tem- 
 porarily hard contains carbon diox- 
 ide, as well as a solid. When we 
 boil it the heat drives off the gas 
 and the solid collects on the sides 
 and bottom of the dish ; thus both 
 are removed on account of the heat 
 and the water becomes soft. How 
 could you show that carbon diox- 
 ide is driven off from temporarily hard water? 
 
 We wash our clothing to remove the visible dirt so 
 that the clothing will be neat and clean. At the same 
 time we remove the invisible dirt which is usually more 
 harmful than the visible. The invisible dirt is composed 
 chiefly of material which has been left by the perspira- 
 tion when it evaporated, particles of dead skin and 
 bacteria. Since the perspiration comes from our bodies 
 it is of great importance that we keep our skin clean 
 not alone visibly clean but really free from anything 
 which can be washed off. The mouths of the tubes 
 through which the perspiration comes, called pores. 
 
PLANTS NEED WATER 105 
 
 should be kept clean and open by frequent baths which 
 ought to be taken daily, if possible. 
 
 Dirt cannot be removed completely without the use 
 of soap. There are two kinds of soap laundry soap and 
 toilet soap. Soap which is suitable for washing clothes 
 and for general housecleaning is usually unfit to be used 
 on the skin. On the other hand, toilet soap, which is 
 intended for tender skin, would have little cleaning- 
 power if used on clothes. See Section 77. 
 
 40. Plants Need Water. 
 
 We all know that plants need water, for if we forget 
 to water them they quickly wilt, and, if they go too long 
 without water they die. If the plants have only wilted 
 they soon take up the water and become stiff and vigor- 
 ous again. In the next section we shall learn the reason 
 for this change. The amount of water which plants 
 need is very great. The water is carried away from the 
 leaves by evaporation,] ust as it is carried from wet clothes 
 which are hung to dry. When we think of the very 
 large surface of the leaves of a tree we will realize that 
 the amount of water which can be given off is enormous. 
 We call the giving off of water from the leaves of a 
 plant transpiration. Transpiration takes place only on 
 the under side of leaves. 
 
 Seeds will not begin to open unless they are supplied 
 with water. Then they swell until they burst, and the 
 young plant comes forth. The amount that seeds swell 
 is always a surprise, as you know if you have ever "put 
 beans to soak." 
 
106 
 
 WATER 
 
 Experiment 52. The Effect of Water upon Seeds 
 and Plants. 
 
 Apparatus: Two glasses large enough to cover a 
 small plant. 
 
 Materials: Beans, a plant in a can or pot, two 
 pieces of cardboard 6"x6". 
 
 a. Fill a glass one-half full of beans and then com- 
 pletely fill the glass with water. Set aside for twenty-four 
 hours and tell what happened. The beans may be dried 
 by putting them in the sun. 
 
 b. Cut a slit in each 
 piece of cardboard from the 
 middle of one side to the 
 center. Slip the pieces 
 around the stem of the 
 plant from opposite sides 
 and press them down upon 
 the top of the flower-pot. 
 Cover the plant with the 
 glass and set it in the sun. 
 The experiment should ap- 
 pear like the illustration. 
 What collects on the glass 
 after an hour or so? 
 Where does it come from ? 
 Why were the pieces of cardboard used? 
 
 41. Capillarity. 
 
 The word "capillary" means "like a hair," that is., 
 very fine. Capillarity is the strange action of liquids in 
 
 Cut supplied through United States Department of Agriculture. 
 
CAPILLARITY 107 
 
 tubes which are as fine as a hair, or even finer. Let us 
 perform some experiments which show capillarity and 
 talk about it afterwards. 
 
 Experiment 53. Examples of Capillarity. 
 
 Apparatus: Several 6" pieces of glass tubing of 
 different diameters, two glasses, lamp wick, block of 
 wood. 
 
 Materials: Cube sugar, red ink. 
 
 a. Fill one of the glasses with water and place the 
 tubes in it. Describe how the water goes up the tubes. 
 A little red ink, added to the water, will make it easier 
 to see the water in the tubes. In which tube does the 
 water go the highest? You can make a very fine glass 
 tube by heating a short piece of ordinary glass tubing in 
 the flame of a wing burner, and then suddenly pulling the 
 two ends as far apart as you can reach. Water will go 
 six or eight inches up such a tube. Try it. 
 
 b. Fill one glass with water and place it upon the 
 block of wood. Now wet the lamp wick thoroughly, 
 wring it as dry as possible and 
 
 bend it over the edge of the 
 glass so that it reaches the bot- 
 tom of the glass, while the 
 other end falls into the other 
 glass placed near the block. The 
 lower glass should be empty. 
 Tell what happens in a few min- 
 utes. What is this an example of? The oil in a lamp 
 reaches the flame in the same way. 
 
 c. Dip one corner of a lump of sugar in some colored 
 
108 WATER 
 
 water and see how quickly the water passes through the 
 whole lump. 
 
 Capillarity acts in all directions.** Thus if we lay .a 
 lamp wick flat upon a table with one of its ends in a little 
 pool of water the other end will soon be wet. Capillar- 
 ity acts faster downward than in any other direction. 
 Can you explain why this is so? When you put a drop 
 of ink upon a blotter, how does it act? What causes it 
 to act in this manner? Think of all the examples of 
 capillarity you can. Bodies must be porous in order 
 that there may be the little holes in which capillarity miv 
 act. If we wish to stop capillarity we must close the 
 holes. 
 
 We have learned that water is necessary for plants 
 and that the soil must be kept damp if we expect the 
 plants to grow well. How do you suppose that the soil 
 holds the water? Did you ever see water put into a 
 saucer which was placed under a flower pot? How did 
 the plant obtain the water? All soils are not the same 
 in their ability to hold, or take up, water and the follow- 
 ing experiment will show the right kind of soil to use for 
 flowers. 
 
 Experiment 54. How Water is Held in the Soil. 
 
 Apparatus: Chalk box, or other small box, with 
 four or five holes in one side large enough to hold stu- 
 dent lamp chimneys, four or five student lamp chimneys, 
 with cheese cloth tied over their smaller ends, pan. 
 
CAPILLARITY IN SOILS 
 
 109 
 
 Materials: Gravel, sand, coarse soil, fine soil, vege- 
 table mold. 
 
 a. Arrange the apparatus as shown in the illustra- 
 tion and have 
 the water cover 
 the ends of the 
 chimneys. Fill 
 each chimney 
 with a different 
 kind of material. 
 In which does!!! 
 the water rise 
 the highest? In 
 which does the water rise the fastest? Which soil would 
 you prefer to have on your farm, if you were a farmer? 
 
 The farmer is very much concerned with capillarity 
 and we will study it some more when we come to Section 
 54, in which we shall learn that the farm is just like a 
 workshop. Capillarity, besides bringing the water to the 
 roots of plants, is one of the causes of the rise of sap in 
 the stalks of plants and trunks of trees. The evapo- 
 ration of water from the leaves aids the rise of sap, just 
 as the burning of the oil in lamps aids the capillarity in 
 the wicks in bringing the oil to the flame. The next 
 
 Cut supplied through United States Department of Agriculture. 
 
110 WATER 
 
 experiment will prove that capillarity acts in plants, as 
 well as showing where the sap rises. 
 
 Experiment 55. Capillarity in Plants. 
 Apparatus : Glass, knife. 
 
 Materials: Red ink, twigs of any tree having flat 
 leaves. 
 
 a. Cut a few twigs and put them immediately into 
 some water which is strongly colored with red ink. Place 
 the glass in the sun and in a draft of air, if possible. At 
 the end of ten minutes remove one twig and split it 
 lengthwise. Where did the colored water go? Remove 
 another twig at the end of half an hour and examine in 
 the same way. Leave another twig for a full day. How 
 do the leaves appear? How did the colored water get 
 through the stem? Make a drawing of the twig, split 
 lengthwise, showing just where the colored water passed 
 through it. 
 
 If the stalks of plants are not woody, they receive 
 their stiffness from the capillary tubes in them being full 
 of water. If the plants do not receive enough water the 
 tubes become empty and the stalks flabby. We say. that 
 the plants wilt. When is a garden hose stiffer, full of 
 water or empty? 
 
 Review Questions, 21. 
 
 1. What was the position of the Great Dipper last 
 night at eight o'clock? 
 
 2. What are the uses of nitrogen? 
 
REVIEW QUESTIONS 111 
 
 3. How is carbon dioxide harmful and in what way 
 is it helpful? 
 
 4. What are some of the oddities of solution? 
 
 5. Name all the uses of water. Which one is the 
 most important? 
 
 6. Why is soft water cheaper to use than hard 
 water although the same price is paid for each? 
 
 7. How can you prove that plants obtain water 
 from below the surface of the ground? How do they do 
 it? 
 
 8. Why is wet earth heavier than dry earth? 
 Which kind of earth would be heavier when wet, a fine 
 earth or a coarse earth? Explain. 
 
 9. Why do farmers break up the soil so that it is 
 fine, before they plant? 
 
 10. Why do our feet become wet when we walk on 
 the wet sidewalk? 
 
THE GUIDE 
 
PLANTS AND ANIMALS. 
 
 42. The Beginning of Plant Life. 
 
 The beginning of all plant life is in 'the seed. As 
 long as the seed remains dry the little plant rests, but as 
 soon as water is absorbed by the seed it cracks open and 
 the tiny plant begins to grow. Let us examine some 
 seeds and learn how the plant gets its first start. 
 
 Experiment 56. The "Pocket Garden." 
 Apparatus: A plate and a saucer. 
 Materials: Blotting paper, seeds of beet, bean, 
 corn, pea, radish, squash. 
 
 a. Lay a square of blotting paper upon the plate 
 
 and upon it place the seeds. Cover the seeds with an- 
 other square of blotting paper and moisten both with 
 water. Now cover all with the saucer. Keep the blotting 
 paper moist but do not have the seeds under water. 
 Cut supplied through United States Department of Agriculture. 
 
 Elem.Sci. 8 
 
114 PLANTS AND ANIMALS 
 
 Keep in a warm place and examine once a day, noting 
 the order in which the seeds sprout. 
 
 b. Make several drawings of each seed, showing 
 the method by which the baby plant comes out of the 
 seed. 
 
 c. Write a description of the roots, stem, and leaves 
 of each plant.* 
 
 Note to teachers: This work may be extended over con- 
 siderable time and many other seeds may be sprouted. The 
 drawing's and descriptions would make a good supplement to 
 the English and art work. 
 
 43. The Testing of Seeds. 
 
 All seeds do not sprout because all of them are not 
 perfect seeds, or have been harmed in some manner. It 
 is of very great importance to the farmer that he obtain 
 good seed, for otherwise he might plant many seeds 
 which would not grow. Thus the crop would be less 
 than it should be and the farm would not be as productive 
 as it might otherwise be. Most farmers now test their 
 seeds because they have learned that a little trouble in the 
 beginning will save them much money in the end. The 
 testing of seeds to see if they will all sprout is called the 
 germination test. 
 
 . Experiment 57. * Germination Tests. 
 
 Apparatus: Shallow wooden tray, tacks, string. 
 
 Materials: Sand, seeds of various kinds from va- 
 rious stores. 
 
 a. Mark off the sides of the box into two-inch spaces 
 and drive a tack at each mark. Now lace the piece of 
 string backward and forward so as to divide the open 
 end of the tray into squares, two inches on each side. 
 
 * Adaoted from Farmers' Bulletin 408, U. S. Dept. of Agriculture. 
 
TESTING SEEDS 
 
 115 
 
 
 . 
 
 Mark the sides of the tray as shown in the illustration 
 and fill the box with dry sand, heaping it a little. After 
 scraping off the sand with a straight stick the tray is 
 ready for planting. 
 
 b. Plant at least five seeds in each square and plant 
 as many kinds of seeds as possible. The seeds should 
 just be covered by the sand. The same kind of seeds 
 which are bought at different stores, or obtained from 
 different places may be considered as different seeds. On 
 a page in your note book mark the kinds of seed and the 
 place from which you obtained them, together with the 
 number of the square in which you planted them. Count 
 the number marked at the left end of any row as tern and 
 add to this the unit number which is marked at the right 
 end of any row. Do not count the zero. 
 
 c. Water the sand, after planting the seeds, by 
 pouring the water upon a piece of paper placed on the 
 sand. Keeo in a wirm room, watering now and then. 
 and watch for the little plants. In about a week all of 
 
 Cut supplied through United States Department of Agriculture. 
 
115 PLANTS AND ANIMALS 
 
 the seeds which are good will have sprouted. Good seed 
 should have every seed sprout. 
 
 44. The Proper Planting of Seeds. 
 
 While good seeds are neces-sary, if they are not 
 properly planted they will not grow well and perhaps 
 not at all. If the seeds are planted too deeply they may 
 die before they can reach the light, while if they are not 
 planted deeply enough they may become dried by the 
 sun and killed by too much light upon the delicate roots. 
 The depth of planting of seeds varies from one-eighth o 
 an inch, in the case of celery seeds, to four inches in the 
 case of the white potato. If the ground is very damp 
 the seeds may be planted less deep than if the ground is 
 quite dry. Why? Sometimes seed beds are shaded 
 from the sun. Can you explain the reason? 
 
 There was no way for man to discover the proper 
 depth of planting except by experimenting. We can now 
 use the knowledge that has been acquired by others and 
 tints save time. However, let us try the experiment on a 
 few different seeds in order to see why it is that the 
 plants do not grow well if the seeds are not planted at 
 the Drooer depth. 
 
 Experiment 58. *The Proper Depth of Planting. 
 
 Apparatus: Several deep, wide-mouthed bottles., 
 such as pickle bottles, black cloth to cover bottles. 
 
 Materials: Loam, seeds of various vegetables and 
 flowers. 
 
THE PROPER DEPTH OF PLANTING. 
 
 117 
 
 a. Sprinkle about an inch of loam in the bottom of 
 the bottle and place one seed of each 
 of four or five different kinds on 
 the surface of the loam, next to the 
 glass so that they can be seen when 
 they are covered with loam. Then 
 sprinkle about an inch more of loam 
 and repeat with the same kinds of 
 seeds as were used on the first layer. 
 Repeat the process until the bottle is 
 full. Other pupils may use different 
 seeds. Water the loam so that it is 
 moist but not wet. Cover the bot- 
 tle, or bottles, with black cloth, so as 
 to shut out the light from the seeds, 
 keep in a warm place, and examine 
 once a day. Do not let the sun shine 
 upon the bottles. 
 
 b. When the seeds begin to sprout 
 mike drawings of the way in which 
 the plant comes out of the seed and 
 the way in which the root turns. Make drawings of 
 what happens to those seeds which were planted too 
 deeply. You will find that the seeds very near the sur- 
 face may grow all right, but you must remember that 
 the sun did not shine upon the loam. Measure the depth 
 which you find is proper for your seeds, and obtain from 
 the other pupils their best results. 
 
 Cut supplied through United States Department of Agriculture. 
 
118 PLANTS AND ANIMALS 
 
 45. The Needs of the Plant. 
 
 We have learned quite a lot about plants and now we 
 are going to gather the information together. Science 
 study is different from some other studies because in 
 science we learn a number of facts concerning some- 
 thing and then gather all these facts together and try to 
 learn how they all are true at the same time. Then we 
 can form an idea of how the subject studied must act and 
 how it would act if conditions were different. This is 
 called drawing conclusions. Let us study an example : 
 We learned in Experiment 36 that air is necessary in 
 order that plant roots may grow. Since plants start 
 from seeds we might think that seeds would not sprout 
 if they were not supplied with air. If we nearly fill a 
 bottle with moist earth and plant a few beans or peas in 
 it, and then stopple it tightly, it will be found that the 
 seeds will not grow. Other peas and beans planted 
 under the same conditions in an open bottle will grow. 
 Then we can draw our conclusion that air is necessary 
 for plant life of any kind. How do water plants get air? 
 
 We are always told to keep plants in a warm place 
 so that they may grow well. Do you think that if seeds 
 are not kept warm they will grow? Draw your conclu- 
 sions from the last paragraph and then try the exper- 
 iment. Place some seeds in moist loa'm and put it in the 
 ice chest, or try the experiment during cold weather. 
 Light, which is so closely connected with heat, is also, 
 necessary for green plants, as we learned in Section 11. 
 
 In the germination tests, which you are making, you 
 are discovering that although water is necessary for 
 plant life, the plants die if they are supplied only with 
 water. They, like animals, require food and they obtain 
 
THE NEEDS OF THE PLANT 119 
 
 their food from the ground. If the ground is not rich 
 the plants will not grow well because they will not be 
 able to obtain enough food. Farmers add plant-food to 
 the ground, where the ground is not rich enough. Any 
 plant-food which is added to the ground is called a fertil- 
 izer. All plant-food must be such as will dissolve 
 in water after it is put upon the ground. 
 
 Thus plants need light, heat, air, water, and food. Do 
 you think that you need much more in order to live? 
 
 Review Questions, 22. 
 
 1. Why do plants grow best in summer? Give sev- 
 eral reasons. Why is the glass of greenhouses some- 
 times covered with white paint? 
 
 2. Why is it bad for a plant to soak the soil with 
 water so that the water stands on the surface of the soil 
 for several hours? 
 
 3. Why does water go into the soil? 
 
 4. If you were buying a farm how would you decide 
 whether the soil was good? 
 
 5. Why do the plants soon die in Experiment 5fi? 
 Which plants live the longer, those from large seeds or 
 from small seeds? 
 
 6. What is the advantage of germination tests? 
 
 7. Why is the sand watered in Experiment 57 by 
 pouring the water upon a piece of paper? 
 
 8. Why is it necessary to know the proper depth of 
 planting? Do you think that a difference of a quarter of 
 an inch would do any harm to a seed which should be 
 planted two inches deep? 
 
 9. Name and discuss all the needs of a plant. 
 
120 
 
 PLANTS AND ANIMALS 
 
 10. Name all your needs besides the needs of the 
 plant and see if they really are necessary. 
 
 46. *Birds. 
 
 In the minds of farmers birds are closely connected 
 with seeds. The birds visit the fields as soon as they are 
 planted and the farmer views them with suspicion. The 
 birds, as a rule, eat very few seeds of farm crops, and 
 they are much more interested in getting" the worms and 
 insects which have been exposed by the cultivaticn of 
 the land. Since many of the insects which the birds eat 
 
 Cut supplied through United States Department of Agriculture. 
 * See Appendix. 
 
BIRDS 
 
 121 
 
 are those which harm the crops, the birds are really the 
 farmers' friends. Nearly one-tenth of the crops are 
 destroyed by insects, even with the birds eating all the 
 insects they can. If the birds were destroyed it would be 
 doubtful if a satisfactory crop could be raised. The birds 
 do eat seeds, but they are very fond of weed seeds so that 
 they help the farmer also in this case. Weeds can grow 
 better than the crops, and they take the water from the 
 soil which the crops need. 
 
 Not only do the birds help the farmer but they also 
 protect the forests to a great extent. Many of the forest 
 trees are easily attacked by boring beetles and ants. The 
 harm which is due to these wood-boring insects is 
 increased by decay which begins to take place around the 
 holes. In Section 48 we will learn more about the decay 
 of trees. The large illustration is the familiar wood- 
 pecker, called the flicker. Like other wookpeckers it is 
 one of the chief 
 preservers of the 
 forests and 
 should be pro- 
 tected in every 
 way. The small 
 illustration is the 
 well -known 
 phoebe whose 
 chief food is 
 harmful insects, 
 the rest of the 
 food being wild 
 fruit. 
 
 Cut supplied through United States Department of Agriculture. 
 
122 PLANTS AXD AXIMALS 
 
 47. "Wild and Garden Flowers. 
 
 The names of the common garden and wild flowers 
 should be learned and associated with them. The only 
 way to do this is to bring a few flowers to school and 
 compare them with the illustrations in the large refer- 
 ence book which tells all about them. Gradually you 
 will learn the names of all the common flowers as well as 
 some of the rarer ones. The best way to learn so that 
 you will remember is to make a collection of the flowers 
 and write a brief description on the paper upon which 
 you mount each flower. Then you can always review 
 your own work and often learn more than you would 
 from just reading a book. The next experiment should 
 be continued until there are no flowers of the neighbor- 
 hood which you do not have in your collection. See 
 which pupil can make the best collection, but remember 
 that "The race is not always to the swift." 
 
 Experiment 59. A Flower Collection. 
 
 Materials: Sheets of soft, unglazed paper cut 
 17"xll", folded so that they are Il"x8^", strips of 
 gummed paper y\" wide. 
 
 a. Take one of your flowers, which should have a 
 long stem but not longer than ten inches, and several 
 leaves, and compare it with the reference book. After 
 you have learned its name and habits arrange it in the 
 prettiest manner possible, on the right side of the fold, 
 having the paper unfolded. Try to remember how the 
 plant was growing and arrange it as it was, because the 
 natural way is always the prettiest. Cut the gummed 
 paper into lengths so that they will pass over the stems 
 
 * See Appendix. 
 
TREES 123 
 
 and have a good hold upon the paper on each side of 
 the stems, when pasted down. Do not use the strips too 
 long nor too plentifully. The flowers and leaves should 
 be fastened so that they cannot move, but too many strips 
 do not look well. After a plant is nicely fastened, cover 
 ; t with the left hand part of the paper and press under 
 several large books until dry. Then write its name and 
 description in the place on the right hand page where 
 there is the most room. 
 
 48. *Trees. 
 
 The value of trees to man is very great. We have 
 learned that trees take in carbon dioxide and give out 
 oxygen. This is of more importance in our cities than 
 in the open country for there are many fires in houses 
 and factories, all of which are producing vast quantities 
 of carbon dioxide. Although the wind blows part of 
 this away and the rain washes some of it into the ground, 
 yet it is most important that we have as many trees as 
 possible in our cities. Trees, as well as all other plants, 
 give off a huge amount of water by transpiration and 
 change the climate of a locality very much. See Sec- 
 tion 40. Trees also reduce the violence of winds. Final- 
 ly, trees are beautiful. 
 
 While trees, are of very great value in cities they are 
 of still greater value to the nation in whose forests they 
 grow. When rain falls upon bare ground most of it runs 
 off, wearing the soil away and doing no good. After the 
 rain is over there is very little water left in the soil, and 
 this soon dries up in the bright sunlight. If the ground 
 is dry there will be no streams or rivers soon after the 
 
 * See Appendix. 
 
124 PLANTS ANT) ANIMALS 
 
 rain has ceased to fall, although the water which ran off 
 the bare ground during the rain may have caused floods. 
 If there are forests, however, the leaves gather much of 
 the rain and cause it to drip slowly to the ground. There 
 it is caught in the mass of dead leaves and twigs and 
 cannot run away. Thus it slowly sinks into the ground- 
 until the soil is wet many feet deep. When the rain 
 ceases the sun cannot cause the water to evaporate 
 bemuse the thick shade of the forest keeps it out. The 
 water slowly passes away by capillarity and thus the 
 streams and rivers flow for a long time. 
 
 The government of the United States has set aside 
 vast forests called National Forests in order to regulate 
 the flow of water, as well as to keep up a supply of 
 wood. The older trees are cut and younger ones are 
 allowed to grow in their places. The chief enemies of 
 the forest are fire and insects. Men, called Forest 
 Rangers, protect the trees against fire, and our friends 
 the woodpeckers, eat the insects. The illustration shows 
 how "frogstools" indicate that decay has begun. The 
 frogstools live upon the trees where insects have made 
 holes in the bark. Just as our skin protects us from 
 bacteria so the bark protects trees from decay. The 
 heirt of a tree may be decayed and the tree will still live, 
 for its r-rowth is on the outside. In what part of the 
 twigs did the red ink rise in Experiment 55? Each year 
 a ring is added around the trunk of a tree, unless decay 
 is taking place on the outside of it, and by counting the 
 rings on the stump of a tree which has been cut down you 
 can tell its age. 
 
 Just as with flowers, we should know the common 
 trees by name. It is not possible to make a collection 
 
TREES 125 
 
 of trees but we can collect the leaves and seeds and per- 
 haps get pieces of the bark and wood. 
 
 Experiment 60. A "Tree" Collection. 
 
 a. Collect the leaves of all the different trees you 
 can find in the neighborhood and mount them in the same 
 way as you mounted the flowers in the last experiment. 
 
 Cut supplied through United States Department of Agriculture. 
 
126 PLANTS AND ANIMALS' 
 
 Look up their names and habits in the reference book and 
 write a brief description of each kind upon the paper 
 upon which you have mounted the leaves. 
 
 b. Try to obtain pieces of trees with the bark on. 
 Saw these lengthwise, and polish them with sandpaper, 
 after they are thoroughly dry. Label them carefully. 
 To keep the collection, a screw eye may be inserted in 
 one end and the samples hung on hooks which are the 
 right distance apart. 
 
 c. A collection should also be made of the seeds and 
 seed cases of all the trees. These may be placed in 
 small cardboard boxes which are properly labeled. 
 
 It would be a good plan for you to write some letters 
 to pupils in other cities and states, telling them what you 
 are doing and asking them to send you samples of flow- 
 ers, leaves, wood, and seeds which grow there and which 
 do not grow near your school. In return you would 
 send samples which they did not have. Of course you 
 would send your best work. 
 
 The seeds of trees grow in an interesting manner as 
 you will see by the next experiment. 
 
 Experiment 61. Planting Tree Seeds. 
 
 Apparatus: Box filled with sand. 
 
 Materials: Acorns and other soft-shelled nuts, 
 seeds of the apple, pear, orange and lemon trees, and any 
 other tree seeds which are easily obtainable. 
 
 a. Plant the seeds or nuts about one inch deep in 
 the sand' and keep it moist. When the seedlings have 
 
REVIEW QUESTIONS 127 
 
 come up they may be transplanted into tin cans filled 
 with good soil, and allowed to grow. There should be 
 openings in the bottom of the cans? Why? Make a 
 drawing of how each kind of tree starts from its seed. 
 
 b. When the little trees are a few inches high they 
 may be taken home and placed in the garden, unless they 
 are trees which cannot live in your climate. In this case 
 they must be kept in the house. 
 
 Review Questions, 23. 
 
 1. How can you show that plants need light? 
 
 2. What is a flame ? How can you prove your 
 answer? 
 
 3. Do all crystals have the same shape? 
 
 4. Name six of the harmful drinks. Do they always 
 show the harm which they are doing? 
 
 5. What causes water to be hard? 
 
 6. How do birds help the farmer? How do they 
 harm him? Which is greater, the help or the harm? 
 
 7. What is the good of knowing the names of 
 flowers? 
 
 8. Parks have been called the "breathing places" of 
 a city. Explain why this is a good name. 
 
 9. If all the forests were burned or chopped down 
 what would be the effect upon the 'country? 
 
 10. Name all the advantages of having forests. 
 
 49. A Queer Plant Yeast. 
 
 All the plants which we have studied, except bac- 
 teria, have been large enough to be seen. All of these 
 visible plants have needed light, heat, air, water and 
 

 128 PLANTS AND ANIMALS 
 
 food in order to live. They have taken in carbon diox- 
 ide and given out oxygen. They have had leaves, flow- 
 ers, stalks and roots, and have grown from seeds. Now 
 we are going to study a very queer plant which has no 
 roots, stalk, leaves, flowers nor seeds. This plant is 
 called yeast and all its needs are sugar and water and a 
 little heat. 
 
 Yeast plants are so small that they cannot be seen 
 by the use of the simple microscope, but it is necessary 
 to use a very powerful microscope. An ordinary yeast 
 cake contains millions of these 
 little plants. If sugar, water, and 
 a little heat are supplied, each 
 tiny plant begins to send out a 
 Httle swelling called a projection 
 which increases in size until it is 
 nearly as large, as the plant itself. 
 Then it breaks off and becomes a 
 separate plant. Such growth is 
 called budding. The illustration 
 shows the process of budding in 
 nine stages. 
 
 When the yeast plants are growing they change the 
 sugar into carbon dioxide and alcohol. The process of 
 changing sugar in this manner is called fermentation. 
 Most yeast cannot grow without sugar. The following 
 experiment will prove that carbon dioxide is produced 
 when yeast grows, while Section 79 will discuss the 
 manufacture of alcohol. 
 
 Experiment 62. Fermentation. 
 Cut supplied through United States Department of Agriculture. 
 
YEAST AND BACTERIA 129 
 
 Apparatus: The apparatus may be as shown in the 
 illustration on page 104, or a pickle bottle may be used in 
 the place of the flask. A box may be used in the place 
 of the ring- stand. 
 
 Materials: Yeast cake, molasses. 
 
 a. Dissolve the yeast cake in a small amount of 
 water and put it into the bottle which should be filled not 
 more than one-third full of lukewarm water. Add two 
 tablespoonfuls of molasses and shake well. Insert the 
 stopple and place the tube in test tube which should be 
 half full of limewater. In a few minutes bubbles will 
 begin to come from the molasses and pass into the lime- 
 water. How do you know that the gas is carbon diox- 
 ide? Compare this experiment with Experiment 41. 
 
 While the first illustra- 
 tion of yeast shows the 
 growth of a single yeast 
 plant, it must be remem- 
 bered that in a mass of 
 yeast the plants will be 
 found in all stages of 
 growth. The illustration^ 
 shows what would be 
 seen if a small mass of 
 yeast were examined un- 
 der a very strong micro- 
 scope. See Section 78. 
 
 50. Another Queer Kind of Plant The Bacteria. 
 
 In several of our lessons we have read a little about 
 the plants called bacteria and have learned that they 
 grow fast in warm, damp places where the sun does not 
 
 Cut supplied through United States Department of Agriculture. 
 
 Elem. Sci. 9 
 
 Orf 
 
 Vii^X 
 
130 PLANTS AND ANIMALS 
 
 reach. We also learned that they may cause disease but 
 that they can be killed by heat, bright sunshine and by 
 antiseptic washes. 
 
 The bacteria are much smaller than the yeasts and 
 can only be seen by the use of a very powerful micro- 
 scope. They need moisture and a little warmth in order 
 to grow, but they can live on almost any kind of food. 
 Each increases in numbers very rapidly, if supplied with 
 food, in a manner somewhat similar to yeasts. Instead 
 of budding, however, each becomes longer and separates 
 in the middle into two bacteria. This method of increase 
 is called fission. Under favorable conditions a single 
 bacterium will produce seventeen million bacteria in 
 twelve hours. 
 
 Bacteria are the cause of many of the more delicate 
 flavors of food. Thus butter and most kinds of cheese 
 owe their peculiar flavor to the growth of bacteria. It 
 is due to bacteria that the nitrogen of the air can be 
 changed into food which is suitable for plants. See 
 Section 31. There are also several beneficial changes irr 
 substances for which we must thank the bacteria. It im- 
 probable that there could be no life if it were not for the 
 effects which are produced by bacteria. Thus we see 
 that they are our friends. 
 
 Some kinds of bacteria are very harmful, and we 
 should learn how to protect ourselves from them. Be- 
 fore studying how to preserve our health let us learn 
 what the bacteria- do to materials upon which they feed. 
 
 51. Souring and Decay. 
 
 When bacteria have been present in food for some 
 time, they change it into substances which have bad 
 odors and flavors.. The food is spoiled and we call this 
 
SOURING AND DECAY 131 
 
 spoiling decay. If the bacteria had not been present 
 there would have been no change at all .in the food. So 
 the bacteria spoil our food and thus are our enemies. If 
 the only effect which the bacteria have upon food were 
 merely to spoil it we would not have to take so much 
 care of it. In addition to spoiling the flavor of our food 
 and causing it to have a bad odor, the bacteria produce 
 certain poisons, called ptomaines. The ptomaines may 
 be formed to a degree sufficient to poison us without 
 there being any disagreeable odor or flavor to the food. 
 These poisons are very dangerous and we should be 
 careful not to eat old food, or food which has remained 
 long in a warm place. Cooking the food does not destroy 
 the ptomaines. 
 
 Another kind of bacteria changes cider and grape 
 juice into vinegar. The mass of slimy material which is 
 always found in vinegar, called mother of vinegar, is com- 
 posed entirely of countless millions of bacteria. Vine- 
 gar is one of the class of materials which are called acids. 
 You can always detect an acid by its sour taste. When 
 milk sours it is because an acid has been produced in it 
 by bacteria. In the following experiment on milk we 
 can learn what is necessary to preserve food of all kinds. 
 
 Experiment 63. How to Preserve Milk. 
 
 Apparatus: Can or dish in which to boil water, 
 ring stand, burner, 4 test tubes or small bottles. 
 
 Materials: Milk, borax, cotton, labels, boiling soda. 
 
 a. Label the test tubes No. 1, 2, 3, 4 and fill them 
 one-half full of fresh milk. Set one aside, just as it is, 
 in a warm place, put the second one in as cold a place as 
 possible. To the third add a pinch of borax and set in 
 
132 
 
 PLANTS AND ANIMALS 
 
 a warm place. The fourth 
 tube should have a plug 
 of cotton put into the top 
 and then it should be 
 placed in the can of cold 
 water which should 
 gradually be heated to 
 176F. and kept at about 
 that temperature for at 
 least five minutes. This 
 heating is called pasteur- 
 ization. Then set it in 
 a warm place. Examine the milk once a day. Which 
 tube sours first? Which keeps sweet the longest? 
 
 b. Add a little boiling soda to some of the sour 
 milk. Notice the bubbles. They are carbon dioxide 
 How does the milk taste? 
 
 The illustrationshows the kind of bacteria which caused 
 the milk to sour. They are very much magnified. 
 
 Bacteria can be killed by heat and by poisons. The 
 poisons are called preservatives, and they should never 
 be used. The experiment was to show that poisons may 
 preserve food but they are harmful and unnecessary. 
 The growth of bacteria may be made very slow by keep- 
 ing the food cold. Since bacteria require moisture in 
 order to live, if the food is dried it may be protected from 
 them. Smoking of meat and fish, as well as drying, will 
 preserve them for a long time. Food may be kept moist 
 and yet free from bacteria by the use of salt, sugar, or 
 spices and vinegar. 
 
 After the bacteria, which are in or on the food, are 
 killed bv heat it is necessary to exclude others. This is 
 
 Cut supplied through United States Department of Agriculture. 
 
DISEASE AND SANITATION 
 
 133 
 
 the reason for sealing preserves and canned goods. Why 
 did you put the plug of cotton in the test tube of milk 
 which you pasteurized? 
 
 If we leave food upon our teeth the bacteria, which 
 are always present, live upon this food and produce acids 
 which hurt the covering of our teeth, called enamel. If 
 this action continues very long the enamel is destroyed 
 and then the bacteria of decay cause our teeth to decay. 
 For this reason we should wash our teeth at least twice 
 a day and always before going to bed. When the enamel 
 is destroyed the repairs which a dentist may make are 
 not lasting because the decay goes on around the filling 
 which he puts into the tooth. Thus the hole or cavity 
 becomes larger and larger until the tooth is destroyed. 
 52. Disease and Sanitation. 
 
 Some bacteria enter the body and, living upon the 
 tissues, produce various diseases. All bacteria which 
 enter the body are not harmful and some are helofiil. 
 Diseases which are given by one person to another by 
 means of bacteria are called contagious. Flies are car- 
 riers of disease and the common house fly, which is 
 shown magnified five times, is one of our worst enemies. 
 
 The life history of the common house fly is very 
 
 Cut supplied through United States Department of Agriculture. 
 
134 
 
 PLANTS AND ANIMALS 
 
 rapid. A single fly lays 
 about one hundred and 
 twenty eggs on the aver- 
 age, in manure and decay- 
 ing material, which hatch 
 within a day, producing 
 maggots or larvae. The 
 larvae or maggots go into 
 the pupal or quiet stage 
 after a few days, from 
 which stage they come 
 forth as flies in less than a 
 week. The puparium is shown to the left of the illustra- 
 tion and the larva to the right. The other illustration 
 shows a blue-bottle fly, .also magnified five times. This fly 
 is also called the meat fly, and breeds in decaying animal 
 matter. All of these flies may carry disease. The com- 
 mon house fly should be called the typhoid fly as it is a 
 carrier of that disease. 
 
 We should protect ourselves from the flies by 
 screens, and do what we can to deprive them of foods. 
 No decaying materials should be allowed anywhere in 
 the yard or neighborhood. Horse stables should have a 
 proper place for storing the horse manure until it can be 
 carried away. Absolute cleanliness is a great preven- 
 tive of flies. Sticky fly paper and fly traps will help to 
 remove the flies which come into the house. 
 
 The diseases which are caused by bacteria are dif- 
 ferent from the poisons which the bacteria produce. The 
 ptomaines act quickly while the diseases take several 
 days, or perhaps weeks, in which to develop. The devel- 
 
 Cut supplied through United States Department of Agriculture. 
 
REVIEW QUESTIONS 135 
 
 opment of a disease which is caused by bacteria is due 
 to their growth within the body. If the body is in a 
 good condition the bacteria will be overcome by forces 
 within the body ; it is usually a weak body which is easily 
 attacked by bacteria. Thus the best way to prevent 
 being- sick is to take good care of the body. This means 
 eating the proper food, sleeping enough and not doing 
 anything which is harmful to the body. It means bodily 
 cleanliness and clean houses. It means good ventilation, 
 plenty of sunlight, and breathing fresh air both day and 
 night. 
 
 Cleanliness, if complete, is the greatest help to sani- 
 tation. Sanitation means freedom from harmful bacteria. 
 Review Questions, 24. 
 
 1. What use is made of nitrogen? 
 
 2. Name all the sources of carbon dioxide we have 
 studied. 
 
 3. What is the use of carbon dioxide? 
 
 4. What are the needs of all living things? 
 
 5. What is yeast? What can yeast do? 
 
 6. What are bacteria? Are all bacteria harmful? 
 
 7. How can you keep milk from souring? Which 
 is the worst way and which is the best way? 
 
 8. Why should we clean our teeth at night when no 
 one is to see them? 
 
 9. Why should we keep clean? 
 
 10. What is the best way to prevent being sick? 
 
 Next year we shall study more about plants and 
 animals. Now we are going to learn about what plants 
 and animals need for food and about the food which 
 thev make. 
 
THE GUIDE 
 
FOOD. 
 
 53. The Source of All Food. 
 
 The source of all of our food is the soil. Plants 
 grow in the soil and, while they take in carbon dioxide 
 through their leaves and nitrogen, after it has been 
 changed by the bacteria, through their roots, they could 
 not live if it were not for other material which is con- 
 tained in the soil. This material is chiefly potash and 
 phosphorus. Animals eat the plants and are used as part 
 of the food of man. 
 
 Plant food and animal food are not very different 
 in regard to the kinds of material which they contain. 
 The difference comes in the proportions in which they 
 occur. We need our food for three reasons : to give us 
 Cut supplied through United States Department of Agriculture. 
 
 . 
 
 0007&/V- 3.3% 
 
 4.0% 
 
 V4LU Pffi POU/V0 
 
 Cut supplied through United States Department of Agriculture. 
 
138 
 
 FOOD 
 
 AS 
 
 strength, to keep us warm, and to store up fat. The 
 material which builds up the muscles and aids in the 
 growth of new tissue is called protein. Lean meat and 
 eggs are examples of food which contain a large amount 
 of protein. Peas and beans are the vegetables which 
 contain the most protein. The materials which 
 are used chiefly for producing our animal heat 
 are called carbohydrates. Grains, potatoes and other 
 starchy foods, and all sugars are composed largely of 
 carbohydrates. Some of the carbohydrates are trans- 
 formed into fat. The fats, both animal and vegetable 
 are used to produce fat in the body but they also produce 
 a large amount of heat. Animal fats are butter, lard and 
 the other fats which form a part of the meat which we 
 eat. The amount of heat is measured by the calorie. A 
 calorie will raise the temperature of one liter of water 
 one degree Centigrade. A liter is the measure of liquids 
 in the French system and is a little more than a quart 
 See Section 58. 
 
 TYPE Of- ST/ILH' YfGSTXBLf. 
 
 7Z2V 
 T- 0.2 
 
 G4/?SO- 
 
 Cut supplied through United States Department of Agriculture. 
 
THE SOURCE OF ALL FOOD 
 
 139 
 
 AS 
 
 Milk is very nearly a perfect food. The illustration 
 shows a glass of milk and the divisions indicate the dif- 
 ferent parts of the milk. Such a drawing is called a 
 diagram. The other illustrations show some common 
 vegetables. Note that there is more water in all of these 
 vegetables than in milk This is true of nearly all vege- 
 tables and fruits, before they are dried. Notice also that 
 vegetables have very little fat. For this reason they are 
 good for summer food, as we need, and should eat very 
 little fat in warm weather. 
 
 In Section 31 we learned that ihe bacteria took in 
 the nitrogen from the air and changed it into food for 
 plants, and that it was this food which if we ate it, 
 
 LETTUCE 
 
 ,45 
 
 CAVL/FLOWE& 
 
 ----- -94.7 '<#> 
 
 0.3 
 
 G4RBO- 
 
 0.3 
 
 ASH 
 
 would give us strength. Protein is the food which the 
 plants make by the aid of the bacteria. So again we see 
 that life would be impossible without our friendly bac- 
 teria. 
 
 Cut supplied through United States Department of Agriculture. 
 
140 FOOD 
 
 54. The Farm a Workshop. 
 
 For a long time people thought of the farm as a place 
 where they could obtain something for almost nothing. 
 All that they had to do was to plant seeds and reap the 
 harvest. When it became necessary, however, to raise as 
 large crops as possible, on account of the increased num- 
 ber of persons who had to be fed, people found that they 
 must consider the farm as a workshop. Just as the ma- 
 terials are manufactured into the finished product in a 
 workshop, so on the farm the food for the plants is made 
 into vegetables and fruits. 
 
 In a workshop the supply of material, which is to be 
 used to manufacture articles, must be kept in large quan- 
 tities and the factories cannot produce the articles unless 
 they have a proper supply of material. In the same way 
 every plant that grows and every fruit or vegetable which 
 is produced require a certain amount of plant-food. This 
 plant-food is taken from the ground never to return. 
 When all the plant-food has been removed by the grow- 
 ing plants, no more plants will grow in that soil. We 
 say then that the ground is sterile. If we wish to 
 change sterile land so that crops may be raised upon it, 
 we must put into the soil the materials which plants 
 require to make them live and grow. Such material is 
 called a fertilizer. 
 
 A good farmer never allows his land to become 
 sterile, but each year he adds to the ground the right kind 
 of plant-food for the crop he wishes to raise. Now you 
 see why a farm should be considered as a workshop if 
 you want a good crop you must either have in the soil 
 those materials which the plants need or else you must 
 
THE FARM A WORKSHOP 141 
 
 put them there. New land usually has a good supply of 
 plant-food. Land which has been used for many years 
 must have fertilizers added to it, if it is to produce good 
 crops. Plant-food is chiefly phosphorus, potash, and 
 nitrogen, although there are many other materials which 
 are needed in small quantities. 
 
 All other kinds of business depend upon the farmers 
 to whom we must look for our food of all kinds except 
 fish. The farmer has opportunities in his business which 
 are far greater than those found in other lines of work. 
 He can, by experimenting, produce new fruits and vege- 
 tables, as well as improve those which we already have. 
 He is a producer, that is, he gives to the world something 
 which the world did not have before. Most of the other 
 kinds of business take what has been produced from the 
 earth and only make from it something which is of use. 
 While all kinds of business tend to make the world a 
 pleasanter place in which to live, the farmer is the only 
 business man who actually makes the world richer for 
 his labor. 
 
 55. Tilling the Soil. 
 
 When we consider the farm a workshop in which 
 plant-food is changed into plants, and fruits, and vege- 
 tables, we must remember that plants require a large 
 amount of water, and take care that they receive it. We 
 learned in Section 48 that if rain fell upon bare ground 
 it all would run off rapidly and wear the soil away. 
 Where the land is level the run-off is not nearly as great 
 as upon a hillside, but so much runs off that the soil does 
 not receive enough to supply the needs of the plants. Tf 
 
142 
 
 FOOD 
 
 the ground is made rough and porous much more water 
 will be absorbed than if the ground has been left smooth 
 and hard. The loosening of soil so that it may catch the 
 rain and prevent the run-off is called tilling. 
 
 The first tilling, in preparing the soil for the seeds, 
 exposes the under layers to the action of the air and also 
 helps to bring more plant-food to the surface. Another 
 necessity for tilling is to put the soil into such a porous 
 and softened condition that the tender roots of the tiny 
 plants may work their way into it. Porous soil also 
 allows more air to enter it. 
 
 All tillage of the soil, after the seeds have been 
 planted, is to kill weeds and to save the moisture which 
 is in the soil. We have learned that water moves 
 
 through the soil by capillar- 
 ity and if we want to stop 
 the movement we must close 
 the holes. If you place 
 some powdered sugar upon 
 a cube of sugar, as shown in 
 the illustration, and then 
 touch the cube to some 
 colored water (red ink) you 
 will see the water rush up 
 the cube but stop when it 
 reaches the powdered sugar. 
 Capillarity is good in the 
 cube sugar but very poor in the powdered sugar. Try 
 the experiment. We can do the same thing to soil by 
 loosening the top of the soil and making it fluffy and 
 
 Cut supplied by the International Harvester Co. 
 
TILLING THE SOIL 
 
 143 
 
 powdery just like the powdered sugar. Such a layer of 
 loose soil is called a mulch. It is only by mulching that 
 the moisture can be kept in the soil. In those countries 
 in which there is very little rain in summer the farmer 
 is able to raise good crops by the proper amount of 
 mulching. 
 
 The first illustration shows that soil which is not 
 mulched cracks open and 
 allows evaportion to take 
 place far below the sur- 
 face. Soil under such 
 conditions will dry very 
 quickly and be of no use for farming. The second illus- 
 tration shows soil which has been properly mulched and 
 
 the moisture preserved. 
 It is very much like the 
 cube sugar and. the pow- 
 dered sugar: the lower 
 soil continues to bring up 
 water from below, while the dry mulch prevents its loss 
 when it comes near the surface. The soil must be 
 mulched soon after each rain, as the water opens the 
 pores of the former mulch and causes it to be of no use. 
 
 Tilling, as has been noted, kills weeds. This is 
 accomplished by the tearing up of the weeds and saves a 
 large amount of water. Weeds, like other plants, use 
 vast quantities of water but they give no return to the 
 farmer. Thus all the water which weeds use is a total 
 loss to the farm. Weeds should be killed for other reasons, 
 the chief one being that they are liable to kill the crops 
 and their seed or stalks may spoil some crops. 
 
 Cuts supplied by the International Harvester Co. 
 
144 FOOD 
 
 56. Irrigation and Drainage of Farms. 
 
 It often happens, in lands of little rain, even it 
 the soil is well tilled and the mulching well done, that 
 there is not enough water in the soil for the proper needs 
 of the crops. Under such circumstances it is necessary 
 to add water to the farm from some river or well. Any 
 addition of water to land is called irrigation. The soil 
 should always be tilled as soon after irrigating as it 
 becomes a little dry on top. Why? 
 
 Irrigation is of the utmost importance, since about 
 two-fifths of the area of the United States is too dry for 
 farming. Up to the present time a little over ten million 
 acres are irrigated, which is very little compared with the 
 dry area. Proper irrigation, that is, where there are 
 several thousand acres to be irrigated, must be under- 
 taken by the government, since it is impossible for any 
 place to build a large irrigation system. Although the 
 cost of irrigation is great, the large crops more than pay 
 for it, and land, which otherwise would be a desert, 
 blossoms into productiveness. 
 
 Sometimes there is too much water in the soil and 
 it is necessary to remove some of it. This removal of 
 water from land is called drainage. Drainage may be 
 accomplished by ditches and by covered drain pipes 
 which allow the water to enter at the joints. When the 
 pipes are used the drainage is called underdrainage. Un- 
 derdrainage is better than surface drainage as it keeps 
 the water at the proper level and the plants send their 
 roots deeper. Thus the plants have more soil from 
 which to obtain their food and therefore they grow bet- 
 ter. What is the harm of having too much water in the 
 soil? 
 
GARDENING 145 
 
 57. Gardening. 
 
 We have been learning about plants and their needs 
 for some time as they are most important, since all life 
 depends upon them. Their needs have been learned in 
 the various topics under light, heat, air, water, and 
 food. We have seen how the soil must be treated in 
 order to supply the needs of the plant in the best manner, 
 and to preserve the water which is in the soil. Now we 
 should put our knowledge into practice, for that is its 
 real test, and by experimenting we may strengthen our 
 knowledge, and also increase it. This experimenting 
 should be performed in the school garden, or in the home 
 garden, or what is best of all, we should put into practice 
 what we have learned about plants both in the school 
 garden and in the home garden. 
 
 The selection of the place for the garden is very 
 important. It should be near enough to the school to be 
 convenient, and if the land has a slight slope toward the 
 south it will be the best location for a garden in which 
 to raise some of the early crops. Why sloping? Why 
 toward the south? Having selected a good location what 
 should be done to the soil before planting the seeds? 
 The pulverizing of the soil should be done to a depth of 
 at least six inches and eight inches would be better. 
 
 Even if the land has not been used as a garden in 
 former years, it is better to put on some fertilizer at the 
 same time as you are breaking up the top of the soil. The 
 very best fertilizer is barnyard manure. A good way 
 in which to apply the manure is to sprinkle a very thin 
 layer of it on the soil and then work it beneath the sur- 
 face with a spade or fork. Barnyard manure, in addition 
 to being an almost perfect food for plants, has the great 
 
 Elem.Sci. 10 
 
146 
 
 FOOD 
 
 Cut supplied through United States Department of Agriculture. 
 
GARDENING 147 
 
 advantage of loosening the soil and making it more 
 porous . Why is this an advantage? Many helpful 
 bacteria which are found in barnyard manure also are 
 added to the soil. If barnyard manure cannot be easily 
 obtained a small amount of commercial fertilizer may be 
 used. 
 
 You should always sow your garden seeds in rows. 
 Straight rows make a garden appear neat. You can 
 obtain a straight line by means of a tight string. Push 
 a stick into the ground where you want to begin a row 
 and tie a string to it. Go ro the other end of the row, 
 drive a stick and tie the other end of the string to it. 
 Where did you use a tight string before? Pows should 
 be about the same distance apart throughout their en- 
 tire length. This can be accomplished by placing the 
 two sticks at the two ends of the second row the same 
 distance from where they were for the first row. How 
 deep are you going to plant your seeds? After planting, 
 the soil should be pressed gently down s6 as to fit closely 
 around the seeds. This gives them the best chance of 
 obtaining water and plant-food from the soil. 
 
 The care of the garden is chiefly to keep it moist, but 
 not too wet, to remove the weeds, and to keep the upper 
 part of the soil loose. Can you give the reason for each 
 of these necessities? When the plants come up they 
 should be thinned, that is, part of them should be re- 
 moved if they are too close togther. Each plant must 
 have room in which to grow and each one must have 
 plenty of sun. Thinning may have to be done several 
 times as the plants grow. \Vhile the sunlight is neces- 
 sary, some plants, especially lettuce, may require to be 
 shaded by boards, placed along the so.uth side of the row,. 
 
148 FOOD 
 
 and held in place by stakes which are driven into the 
 ground. 
 
 The illustration gives a plan for a garden on a city 
 lot, about fifty by ninety feet, and shows one method of 
 following early crops with late crops. The plan will 
 depend upon the locality. Full directions for planting 
 will be found on each envelope of seeds* You have 
 learned in general what to do, and you have also learned 
 why you do it. 
 
 Review Questions, 25. 
 
 1. What effect has sunlight upon plants? How 
 can you prove your answer? 
 
 2. Are there any plants, either large or small, 
 which are harmed by sunlight? Is this an advantage to 
 us or is it a disadvantage? 
 
 3. How can you prove that plants require heat in 
 order to grow? 
 
 4. How do you know that plants need air? What 
 part of the air do the leaves take in? What part of the 
 air do the roots use? Can the roots take this part of the 
 air without some help? Explain. 
 
 5. How do plants help man? 
 
 6. How do plants obtain the water which they need 7 
 What is the harm of too much water? 
 
 7. Do all plants grow in the ground? Explain. 
 
 8. Tell about the harmful plants. What can we do- 
 to protect ourselves from them? 
 
 9. Name the three kinds of food' material: fop man. 
 
REVIEW QUESTIONS 149 
 
 Give some examples of each kind, and tell the use of 
 each kind, 
 
 10. Explain how water can be kept in the soil. 
 What is meant by 'dry farming"? Is the farm dry? 
 
 Thus far in our science work we have been learning 
 about the necessities of life: now we shall study some of 
 the things which help to furnish the comforts and con- 
 of civilization. 
 
THE GUIDE 
 
MECHANICS. 
 
 58. Simple Measurement. 
 
 The first -measurement we are interested in is that 
 of length. We want to know how tall we are, how high 
 a building or a mountain is, and how far it is to a cer- 
 tain place. When you say that you are four feet tall you 
 mean that you are four times as long as the foot meas- 
 ure. You compare your length with this length which is 
 twelve inches. The foot measure is your standard 
 When you measure the length of a building you find how 
 many times the twelve inches are contained in the length 
 of the building. Thus you really divide the length of the 
 thing you are measuring by the length of the standard. 
 Where the comparison of two objects can be expressed 
 as numbers the comparison is always division. 
 
 Our common standards of length are the foot, yard, 
 and mile. Other countries have different standards, and 
 we are gradually coming to use the French system. The 
 chief advantage of the French system is that it is a deci- 
 mal system. Thus 10 millimeters make a centimeter; 
 10 centimeters make a decimeter; and 10 decimeters 
 make a meter. For most science work we use the 
 centimeter. There are no eighths, sixteenths, and other 
 divisions to bother us in our work. We do not have to 
 remember that 3 feet make a yard, and that 5*/2 yards or 
 16J/2 feet make a rod. We are liable to forget the odd 
 numbers and they are hard to multiply and divide. The 
 
152 MECHANICS 
 
 entire French system is decimal as we shall see later in 
 our science. 
 
 The next measurement after length is area. Area 
 is the surface of the thing measured and is found by 
 multiplying the length by the width, if the surface has all 
 right angles. How many degrees in a right angle? We 
 express area in square feet, square yards, or square miles. 
 We also have another standard called the acre. Can yon 
 tell how many square feet there are in an acre? Not an 
 easy number to remember, is it? Many of our standards 
 are not very convenient but we do not think much about 
 them since we have always had them. It is only when 
 we learn of a better method of doing something that we 
 realize how much we have missed up to that time. The 
 French acre, while it is about two and one-half times as 
 large as our acre, is 100 meters long and 100 meters wide. 
 This makes 10,000 square meters and is much more easily 
 remembered than the number of square feet in our acre. 
 For science work we use the small measure as in the case 
 
 of length. It is the square centimeter. 
 - Next after area is volume. Volume is the 
 
 space occupied by a solid body or it is the 
 space within a hollow body. The volume of a 
 [sol body having its sides at right angles to one 
 (1"| another can be obtained by multiplying to- 
 gether its length, width, and depth. The result 
 is expressed in cubical measure, such as cubic 
 inches, cubic feet, cubic yards, and, in the case 
 of wood, as cords. How many cubic feet in a 
 cord? The French system uses the cubic 
 meter. For ordinary science work we shall 
 use the cubic centimeter. A measure like the 
 
MEASUREMENT 153 
 
 illustration, which is marked in cubic centimeters is 
 called a graduate. This is intended for liquids. 
 
 When we are using the French system we should 
 not compare it with the English standards which 
 we use, but should take it just, as it is, that 
 is, the same as a Frenchman would use it. How- 
 ever, in order to know what are the real values of the 
 French units you should learn the following: 1 centi- 
 meter equals .39 inch, 1 meter equals 39.37 inches, and 1 
 kilometer or 1000 meters (the French mile) equals .62 
 mile. 
 
 Experiment 64. Measurement. 
 
 Apparatus : Rule one foot long, marked in inches 
 and sixteenths, and in centimeters and millimeters, rec- 
 tangular pieces of cardboard of various sizes, cubical 
 blocks of wood of various sizes, empty boxes of various 
 sizes, which are water tight, graduate, several circular tin 
 cans, string. 
 
 a. Find the length and width of a piece of card- 
 board in inches and sixteenths. Now find the area. 
 Measure the same piece of cardboard in centimeters and 
 millimeters. Put down the number of millimeters to the 
 right of the decimal point. Now find the area. Which 
 is easier to use, the French system or the English? 
 
 b. Measure another piece of cardboard, using the 
 French system and compare its area with the area of the 
 first piece. That is, divide the area of the large piece by 
 the area of the smaller piece, carrying the number out to 
 two decimal points. Now measure the second piece of 
 cardboard in the English system and compare its area 
 with the area of the first piece, also in the English sys- 
 
154 MECHANICS 
 
 tern. The answer should be nearly the same but there 
 will be an error due to wrong measurement. You see it 
 makes no difference what standards you use, for the real 
 size of the body remains the same. Remember the two 
 kinds of thermometers. 
 
 c. Find the volumes of two blocks of wood by using 
 the French and the English systems. When you get 
 through you will have no doubt in your mind which 
 standards are the easier to use. Compare the two 
 volumes. How much larger is one block than the other? 
 
 d. Find the volumes of two boxes, in the French 
 system only. Compare the two volumes. Using the 
 graduate, see how many cubic centimeters of water are 
 required to fill each box. How do these amounts com- 
 pare with the answers which you obtained by multiplica- 
 tion? 
 
 e. Measure the diameter of a circular tin can and 
 multiply it by 3 1-7 and by 3.1416. Then measure the 
 distance around the can with a string and compare the 
 length of the string with your answer. Which is more 
 nearly correct, the answer obtained by multiplying the 
 diameter by 3 1-7 or by 3.1416? 
 
 59. Everything has Weight. The Balance. 
 
 Whenever we try to lift any object we feel a ' pull 
 which we must overcome if we are to move it. We call 
 this pull toward the earth the weight of the object. We 
 say that the force of gravity pulls the object and the earth 
 together. In Section 63 we shall learn more about forces. 
 The force of gravity pulls directly toward the center of the 
 
EVERYTHING HAS WEIGHT 155 
 
 earth, and unless an object rests 
 upon something it will fall in that 
 direction. If we wish to balance 
 anything so that it will stand erect 
 we must have either a large place 
 upon which the object rests or we 
 must have most of its weight be- 
 low the place upon which it rests. 
 The illustration shows you how you ^_ ___ 
 can balance a pencil upon its point 
 by means of a knife. Explain the 
 reason for this. 
 
 Since everything has weight, people have used 
 weight as a method of measuring material, for a long 
 time. v: Just as there are standards for length, area, and 
 volume, So there are standards for weight. The com- 
 mon English standards are the pound and ton, and they 
 have no special meaning. The French units are the 
 gram and kilogram (100 grams) and mean something. 
 The gram is the weight of one cubic centimeter of 
 water at 4C. and the kilogram is the weight of 1000 cubic 
 centimeters of water at 4C. This gives two ways of 
 measuring water. It may be measured in a graduate or 
 it may be weighed. The number of cubic centimeters 
 and the number of grams will be the same. In the Eng- 
 lish system the weight of a cubic foot of water is 62.4 
 pounds at 4C. There is no connection between any 
 two parts of the English system and many different num- 
 bers must be remembered in order to change from one 
 unit to another. The French system of weights is also 
 decimal and there is nothing to remember. The weights 
 are always expressed in parts of a kilogram or parts, of a 
 gram. 
 
156 
 
 MECHANICS 
 
 Experiment 65. *Making a Balance and Weighing. 
 
 Apparatus: Hammer, saw, plane, bit-stock, bits 
 y%" and *4", sandpaper, file, pair of pincers, set of 
 weights (French system). 
 
 Materials: Soft pine board %" thick, 12" long and 
 
 * Adapted from Farmers' Bulletin 408. U. S. Dept. of Agriculture 
 Cut supplied through United States Department of Agriculture. 
 
THE BALANCE 157 
 
 10" wide, another board X" thick, 10" long and 4" wide, 
 two nuts having a half inch hole, screw eye, four Y% 
 metal screws, iron or soft brass wire No. 12, pieces of 
 tin, old knife blade, one dozen ]/%" screws ^" long, fine 
 needle. 
 
 a. The illustration shows the balance as it should 
 appear when finished. The, base (a) is 12"x 7", the pil- 
 lar (b) is^;" square and .9" high, and is set in a J/" 
 hole in the center of base. The upper end of the pillar 
 should be sharpened to an edge as shown at (k), and a 
 slot sawed in it as shown at (1). The beam (c) is made 
 from a stick %" square and .10" long. Its lower edge is 
 left straight but the other. sides are planed so as to make 
 the ends a little larger than half an inch square. The 
 ends are then rounded so that the nuts (e) will screw on 
 snugly. A notch 1" wide and : ^" deep is cut in the cen- 
 ter of the bottom edge. This receives the central bearing 
 of the beam. An inch from each end of the beam a 
 notch J^" deep is cut to receive the tray bearings (n). 
 The two tray bearings, as well as the pillar bearing, 
 should have the notches lined with tin as shown at (m) 
 and (o), A pointer (f) made of J4" material, is firmly 
 fastened to the beam by two screws. Its lower end is 
 provided with a needle, colored black so as to be easily 
 seen. The screw eye (h) is placed near the end of the 
 pointer and in the center of the pillar. It should turn 
 easily. When the balance is completed, turn the screw 
 eye so as to hold the pointer firmly, then paste to the 
 pillar back of the pointer, a strip of water paper (g), 
 bearing scale marks 1-16" apart, with the zero mark of 
 the scale directly back of the needle. 
 
 The bearings of the balance are the most important 
 
158 MECHANICS 
 
 part of the instrument. The knife edge (1) may be made 
 of a pocket knife blade or of a piece of hard brass filed 
 to a straight sharp edge. The knife edges for the tray's 
 bearings (n) are made by filing the under side of the tray 
 wires where they cross the beam. The tray wires are 
 made of No. 12 wire. The trays (d) are 3"x3" and J4" 
 thick. Two holes near the opposite edges receive the 
 wires which should be bent in the opposite directions be- 
 neath the trays, thereby holding them firm and level. 
 When the instrument is finished it may be made to bal- 
 ance, that is, the needle may be caused to move to, and 
 remain at, the zero point, by moving the nuts on the ends 
 of the beam toward the lighter side. The whole instru- 
 ment may be made level and steady by means of the four 
 screws at the corners as shown in the illustration, 
 although this is not absolutely necessary. A paper box 
 (j) may be used for small objects. The other tray must 
 have an equal weight placed upon it and the instrument 
 must be balanced before weighing any object. 
 
 b. Place the object which is to be weighed, upon the 
 lefthand tray, and upon the righthand tray place a weight 
 which is a little more than necessary. Then remove this 
 weight and put on the next smalkr weight. If this is 
 too little, add the next smaller weight. Continue this 
 until the instrument balances. The pointer must always 
 swing free of the screw eye. If, instead of using the 
 large weights first, the small ones were used there would 
 be no small ones left to make the final balance. Always 
 begin with the large weights. 
 
EVERYTHING OCCUPIES SPACE 
 
 159 
 
 60. Everything Occupies Space. 
 
 We have no doubt that solids and liquids occupy 
 space and we would not try to put one solid in the space 
 which another solid is occupying. Yet we might think 
 that 'a solid could be placed in a liquid without forcing 
 the liquid away, since the liquid does not always show 
 that its surface has risen. Do you remember how the 
 crow obtained his drink of water from the deep dish 
 which had only a little water in it? Putting one kind of 
 material in the place of another is called displacement. 
 
 It is very hard to realize that gases occupy space but 
 they: do, as we shall see in this experiment. 
 
 Experiment 66. Displacement of Water by Solids 
 and Air. 
 
 Apparatus: Two glasses, stone, block of wood, 
 string, funnel, glass tube, rubber tube, large bottle or jar, 
 graduate, rule. 
 
 a. Note the level of the water when one glass is 
 
 about half full of water, and then lower the stone as 
 shown in the illustration. What happens to. the level of 
 the water? Explain. 
 
160 
 
 MECHANICS 
 
 b. Repeat, using a block of wood. Do floating 
 bodies displace any water? Do they displace as much 
 as they would if they sank? 
 
 c. Measure the block of wood in centimeters and 
 find how many cubic centimeters it contains. Then fill 
 a glass completely full of water, place the glass in an 
 empty jar, or in a deep saucer, and push the block beneath 
 the surface of the water in the glass. The amount of 
 water which overflows should contain very nearly the 
 same number of cubic centimeters as you have just 
 obtained from measuring the block. Measure the water 
 carefully with the graduate and see how exactly you have 
 
 performed the experiment. Now 
 you can tell how to measure the 
 volume of a stone or any irregular 
 body. Explain. 
 
 d. Arrange the apparatus as 
 shown in the illustration and push 
 the funnel deeper and deeper into 
 the water. Does the water go up 
 into the funnel? Does air occupy 
 space? Can you explain what 
 happens in the bent tube? 
 
 61. Density. 
 
 People have long used the sayings "As heavy as 
 lead" and "Light as feathers" without meaning just what 
 they said. They really meant to say that a certain 
 volume of feathers is much lighter than the same volume 
 of lead. When we tell how much a certain volume of a 
 material weighs we are giving its density. Since equal 
 
DENSITY 161 
 
 volumes of feathers and lead do not weigh the same, 
 people should say that lead has a greater density than 
 feathers. How would a pound of feathers compare with 
 a pound of lead? 
 
 We are often more interested in knowing the density 
 of materials than in knowing their weight. The density 
 can always be obtained by dividing the total units of 
 weight by the total units of volume, and is expressed as so 
 many pounds per cubic foot, so many ounces per cubic 
 inch, or so many grams per cubic centimeter, or, in fact, in 
 any units of weight and any units of volume. Thus we 
 say that the density of water is 62.4 pounds per cubic 
 foot or nearly .6 of an ounce per cubic inch, or 1 gram 
 per cubic centimeter. Which is the simplest expression? 
 
 Experiment 67. Density. 
 
 Apparatus: Balance, set of weights, blocks of wood, 
 pieces of stone, brick, lead, iron, zinc, or any kind of 
 material weighing not over '200 grams; glass, large jar, 
 graduate. 
 
 a. Weigh each object and make a record of the 
 weights. Find the volume of each object by means of the 
 displacement of water and record the volumes. Divide 
 the units of weight of each object by the units of volume 
 of the same object. This gives the density of each object. 
 
 How do your answers compare with densities which 
 are given in the table? If they are not quite close, repeat 
 using other pieces of the material. 
 
 You should arrange your work as follows: 
 
 Elem. Sci. 1 1 
 
162 
 
 MECHANICS 
 
 Weight 
 (in grams) 
 
 Name of object 
 
 Aluminum 
 
 Bone _... 
 
 Brass . 
 
 Cork 
 
 Glass 4 m 
 
 Iron 
 
 Lead 
 
 Pine __... 
 
 Stone _.. 
 
 Zinc .. 
 
 Volume Density 
 
 (in cubic (grams 
 
 centimeters) per c. c,) 
 
 ? 2,6 
 
 ? 1.9 
 
 ? 8.4 
 
 ? .24 
 
 ? 2.5 
 
 ? 7.7 
 11.3 
 
 ? .55 
 
 ? 2.6 
 
 ? 7. 
 
 62. Drawings, 
 
 In all science work it is very desirable to illustrate 
 the experiments, which you write up r by means of draw- 
 ings. Drawing is like writing, since we use both to 
 express on paper the ideas which we wish to keep in 
 good form, but drawing is often a better means of expres- 
 sion than writing as it sometimes is impossible to write,, 
 or even explain by speecn, some idea which we have. 
 There are two kinds of drawing; that made without 
 instruments called freehand drawing, and that made with 
 instruments called mechanical drawing. In science work 
 mechanical drawing is used more than freehand drawing, 
 
DRAWINGS . 163 
 
 The chief instruments for mechanical 
 drawing are the rule, square, triangle, and 
 compass. A cheap kind of compass is 
 shown in the illustration. The rule is 
 used for making straight lines, the .square 
 for forming right angles, triangle for 
 obtaining different slants or angles, and 
 the compass for drawing circles or parts 
 of a circle. All that you need in your 
 science work is a rule and a compass. 
 The longest distance across a circle is its 
 diameter and the distance from the cen- 
 ter of the circle to the outside of the circle 
 is called the radius. 
 
 If you wish to make copies of your 
 drawings the following experiment shows 
 one method. 
 
 Experiment 68. Blue Prints from Tracings. 
 
 Apparatus: Piece of window glass a little larger 
 than the drawing which is to be copied, thumb tacks. 
 
 Materials: Tracing paper, blue-print paper. 
 
 a. Make the drawing upon any kind of paper and 
 then cover it with a piece of tracing paper, fastening it 
 with thumb tacks. Trace the drawing with a very soft 
 pencil so that the line will be very dark. Use the rule 
 and compass when tracing just as you would in the first 
 drawing. After the tracing is made, place a piece of 
 blue-print paper upon a board or book and lay the trac- 
 ing upon it, right side up. Cover both with the piece 
 of window glass and expose to the sun until the blue- 
 print paper has become a bronze color. See Experiment 
 
164 MECHANICS 
 
 14 for full directions for the use of blue - print paper. 
 Section 70 tells how to make blue-print paper. 
 
 Review Questions, 26. 
 
 1. How many hours of sunlight were there yester- 
 day? How many hours without sunlight were there last 
 night? 
 
 2. What is the direction of sunset now? How can 
 you tell the direction of sunrise without seeing the sun 
 rise? 
 
 3. What is a flame? Prove your answer. Why 
 does charcoal burn without a flame? 
 
 4. What are some of the ways of keeping food 
 from spoiling? Which is the worst method? Why? 
 
 5. Why is the farmer's occupation the most im- 
 portant? Explain. 
 
 6. What are some of the advantages of the French 
 system of measurement? 
 
 7. Explain why it is better to use the larger weights 
 before using the smaller ones in weighing. 
 
 8. When you blow through a tube into a liquid 
 what is inside the bubbles? What does this show? 
 
 9. What is meant when it is said that the density of 
 one body is greater than that of another body? 
 
 10. Besides talking and writing, how else can you 
 express an idea? 
 
 63. Forces. 
 
 Any push or pull is called a force. Weight is a pull 
 between the object and the earth and, as we have learned, 
 is called the force of gravity. When we say that a body 
 weighs five pounds we mean that the pull between the 
 
FORCES 165 
 
 body and the earth is five pounds. It would be neces- 
 sary to pull the body, from on top, with a force of five 
 pounds, to keep it from falling, or we could accomplish 
 the same result by pushing the body from underneath. 
 We have used a balance to find out the weights of bod- 
 ies. In that case we compared the weight of an object 
 with the weight of some standard. That is we com- 
 pared pulls. 
 
 Some bodies move as a whole, that is, if one part is 
 pushed or pulled so that it moves the whole of the mass 
 moves. Other bodies, such as rubber and thin pieces of 
 many kinds of material, may be moved in one part while 
 the rest remains motionless. If we fasten a 
 rubber band at one end we may move the 
 other end a considerable distance without 
 causing the fastened end to move. When the 
 end, which has been moved, is released it 
 will return to its former position. Bodies 
 which act like this are elastic. Thin pieces of 
 wood fastened at one end, may have the othei 
 end bent quite a distance to one side without 
 breaking. The amount of stretching or bend- 
 ing depends upon the pull. If a weight of five 
 grams bends the stick or stretches the rubber 
 one centimeter, ten grams will cause a move- 
 ment of two centimeters. This gives us an- 
 other method of weighing. 
 
 Experiment 69. Weighing by Elasticity. 
 
 Apparatus: Ring stand, spring from an 
 old window roller, or some brass wire No. 
 20; rule, set of weights, spring balance as shown in the 
 illustration, string. 
 
166 MECHANICS 
 
 a. Fasten about six inches of the window-roller 
 spring to a ring of the ring stand by means of string and 
 bend the bottom turn of the spring into the form of a 
 hook. Holding the rule against it, hang a ten gram 
 weight upon the spring by means of string. How much 
 is the spring stretched? Hang a twenty gram weight 
 upon the spring and see how much the total stretch is. 
 Repeat with the twenty and the ten together. Does the 
 stretch vary with the pull? Does the spring always return 
 to its first position when the weights are removed? If you 
 cannot obtain a roller spring you may wind enough 
 brass wire upon a round pencil to make a roll 
 about six inches long. 
 
 b. Examine the spring balance. Are the division 
 marks the same distance apart? Is this right? Explain. 
 When you weigh anything on a spring balance what are 
 you really measuring? 
 
 A pull tends to separate the parts of a body. We 
 say we can pull something apart. A push tends to make 
 the parts of a body closer together and we often speak of 
 pushing things together. When we push the parts of a 
 body closer together we say that we compress the body. 
 Compression requires force and the force which is needed 
 increases with the surface of the body. It takes more 
 force to compress a body of three square centimeters of 
 area than a body of one square centimeter of area, in fact 
 it takes three times as much force. Yet the force for each 
 square centimeter is the same in both cases. We call 
 the force per unit of area pressure. The pressure needed 
 to accomplish a certain compression is always the same 
 for the same body, but the total force which is needed 
 increases with the area. 
 
THE PLUMB-BOB AND THE PENDULUM 
 
 167 
 
 64. The Plumb-bob and the Pendulum. 
 Since the force of gravity acts toward the center of 
 the earth, and since a tight string makes a straight line, 
 we can easily obtain a line, which if con- 
 tinued would pass to the center of the 
 earth, by hanging a weight on ''he end of 
 a string. This is called a plumb-bob and 
 the direction of the line is called vertical. 
 The name "plumb" comes from the Latin 
 and means lead. This was the best mate- 
 rial for plumb-bobs in olden times. We 
 should make the wall of our buildings ver- 
 tical and we can do it by using the simple 
 method which is shown in the illustration. 
 As you have learned, the surface of 
 water is level. Another name for level is 
 horizontal. How many degrees are there 
 between a horizontal line and a vertical 
 line? Float a piece of wood upon some 
 water in a dish and hang a plumb-bob in 
 
 the water, as shown in 
 the illustration. Then 
 measure the number 
 of degrees there are 
 between the direction 
 of the wood and the di- 
 rection of the plumb- 
 line. See Section 81. 
 If we swing our 
 plumb-bob we have a 
 --_ pendulum. You read 
 in Section 8 that the 
 
168 
 
 MECHANICS 
 
 wheels of a clock are allowed to turn slowly by means of 
 a pendulum. Now we are going to see why a clock can 
 be regulated by the length of its pendulum. 
 
 Experiment 70. The Pendulum. 
 Apparatus: String, stones of various sizes, rule, 
 a. Hang up a small stone by a string 25 centi- 
 meters long and count the number of swings per minute. 
 Tie on a large stone in place of the small stone, keeping 
 the length of the pendulum the same. Does the weight 
 of the stone make any difference in the number of swings 
 per minute? The time that it takes a pendulum to swing 
 from one side and return again to its 
 first position is called the time of 
 vibration. 
 
 ,* b. Hang up a stone, making the 
 I string 100 centimeters long and count 
 the vibrations per minute. How does 
 the number compare with the result 
 obtained in (a) above? If you want a 
 clock to go faster would you lengthen 
 or shorten the pendulum? The illustra- 
 tion shows a clock pendulum. The pend- 
 ulum is kept in motion by the push o/ 
 the projections on the wheel, but the 
 time is regulated by the length of the 
 pendulum. Do you think that a clock 
 would go faster or slower in hot 
 weather? Explain. See Section 18. 
 
 65. The Lever. 
 
 A stick, supported at a point between 
 
THE USE OF THE LEVER 169 
 
 its ends, is called a lever. The point of support is namrti 
 the fulcrum. The advantage of the lever is to obtain a 
 large force by the use of a small force. Let us learn by 
 experimenting. 
 
 Experiment 71. The Use of the Lever. 
 
 Apparatus: Long rule, or stick marked with equal 
 divisions, triangular piece of wood to serve as a fulcrum, 
 set of weights. 
 
 a. Arrange the apparatus as shown in the illustra- 
 
 1111 A ... I ....... 
 
 I - I 
 
 tion. Does it balance? Multiply the smaller weight by 
 its distance from the fulcrum and compare the result 
 obtained by multiplying the larger weight by its distance 
 from the fulcrum. It is not safe to draw your conclu- 
 sions, or form an opinion from one experiment. There- 
 fore place these two weights, and also other weights, at 
 different distances from the fulcrum so that they balance 
 and compare the products as suggested above. What 
 are vour final conclusions? 
 
 This experiment shows you how you can use a small 
 force on the long arm o a lever and exert a large force 
 on the short arm. Notice that the small force has to act 
 a greater distance than tfie large force. You have seen 
 men lift large rocks out of the ground by means of bars 
 of iron called crowbars. You use a lever, or two of them, 
 
170 
 
 MECHANICS 
 
 when you cut cloth or use a nutcracker. Where is the 
 easiest cutting done, near the fulcrum or at the tip of the 
 scissors? If you want to crack a hard nut where in the 
 nutcracker do you place it? The lever is called a ma- 
 chine since it enables man to use a small force to over- 
 come a large force. It is the simplest machine we have 
 and: has been known for countless centuries. See Sec- 
 tion 80. 
 
 66. The Inclined Plane. 
 
 r 
 
 Another machine which is very simple and has been 
 known as long as, if not longer than, the lever is the 
 inclined plane. This is simply a board with one end 
 higher than the other. Instead of lifting a weight verti- 
 cally it is pushed or rolled up the slanting board. Since 
 the force acts a longer distance up the plane it is not as 
 great as it would be if it acted only vertically. How is 
 this like the lever? 
 
 Experiment 72. The Use of the Inclined Plane. 
 
 Apparatus : As 
 shown in the 
 illustration, rule. 
 
 a. Find the 
 weight of the car 
 with its load of 
 stones or weights. 
 Find the force 
 which i s neces- 
 sary to pull the car up the inclined plane. Which is 
 greater? 
 
THE INCLINED PLANE AND WEDGE 171 
 
 b. Make the inclined plane steeper or less steep and 
 find the pull necessary to pull the car up it. Measure the 
 length of the plane and the height of the high end of the 
 plane. Multiply the pull up the plane by the length of 
 the plane and compare it with the result obtained by 
 multiplying weight of the car, with its load, by the height 
 of the end of the plane. Should you draw your conclu- 
 sions from this? Finally draw your conclusions. Cm 
 you see any relation between the lever and the inclined 
 plane? 
 
 A very common use of the inclined plane is made in 
 splitting stumps. The inclined 
 plane in this case is called a 
 wedge. Instead of anything 
 moving up the inclined plane the 
 inclined plane, the wedge, moves 
 and the material has to separate 
 as the wedge is driven into it. 
 The advantage is just the same 
 as in the last experiment. Many ^? 
 other machines are very much 
 like the lever and the wedge, although they are given 
 other names. We shall learn more about machines next 
 year, but it is most important to know just how these two 
 aid us. 
 
 Review Questions, 27. 
 1. Why is the image of an object in a mirror right 
 
172 MECHANICS 
 
 side up, but in a pinhole camera upside down? 
 
 2. What are the sources of heat and light? Can you 
 obtain heat without light, or light without heat? 
 
 3. What is a porous body? Can it be changed so 
 as not to be porous? Is there any advantage in having 
 bodies porous? Name one very important porous body. 
 
 4. Name all the uses of water. 
 
 5. What should we do if we wish to keep in good 
 health? 
 
 6. If a clock is going too slowly, what should you 
 do to regulate it? Explain. 
 
 7. What is a force? What can forces do? 
 
 8. Name two ways by which you can exert a large 
 force by using a small force. 
 
 9. What effect have forces upon elastic bodies? 
 What use is made of this effect? 
 
 10. What are machines? What are the uses of 
 machines? 
 
THE GUIDE 
 
MAGNETISM AND ELECTRICITY. 
 
 67. The Lodestone. 
 
 There are two kinds of material which have the 
 power of pulling bits of iron to them without first touch- 
 ing the iron. These are called magnets. There are 
 natural magnets and magnets which have been made by 
 
 man. The illustration shows a 
 piece of natural magnet which 
 has attracted iron filings to its 
 two ends. Natural magnets are 
 black stones and were first found near Magnesia in Asia 
 Minor. A natural magnet is called a lodestone. The 
 word "lodestone" means leading stone, for if a piece of 
 lodestone is hung up by a fine thread, one end will point 
 nearly north, and thus the lodestone will direct or lead 
 us. The ends of the lodestone where the iron filings are 
 the thickest, are called its poles. The poles ire named 
 north and south because one will point north and the 
 other will point south. The poles of a magnet attract 
 iron with greater force than any other part of the mag- 
 net. Lodestones are not important and are interesting 
 only because they were the first magnets which were dis- 
 covered by man, and their mysterious power has never 
 been fully understood. 
 
MAGNETIC MATERIALS 175 
 
 68. Steel Magnets. 
 
 Magnets which are made by man 
 are called artificial and are much 
 stronger than the natural magnets. 
 All artificial magnets are made from 
 steel. A straight magnet is called a 
 bar magnet, while a straight bar, 
 which has been bent into the form 
 of a horseshoe, is called a horseshoe 
 magnet. The illustration shows a 
 horseshoe magnet. The chief ad- 
 vantage of this form is that both 
 poles can pull upon or attract the 
 same piece of iron. The piece of 
 iron, which is shown across the 
 poles of the horseshoe magnet, is 
 called a keeper. It retains or keeps 
 the magnetic strength. 
 
 Experiment 73. Magnetic Materials. 
 
 Apparatus: A bar magnet, pieces of every kind of 
 material you can find, sheet of paper, thin piece of wood, 
 piece of window glass and any sheet metal. 
 
 a. Try to pick up pieces of every kind of material 
 with your magnet. What can you pick up with it? If 
 you try to pick up a piece of tin with the magnet you 
 must remember that "tin" is iron covered with tin. Iron 
 is sometimes covered or plated with copper and brass. 
 What are your final conclusions in regard to the kind of 
 material which is attracted by a magnet? 
 
176 MAGNETISM AND ELECTRICITY 
 
 b. See if the magnetism will pass through a piece of 
 paper, thin wood or thin glass, or thin sheets of metal. 
 
 The space around a magnet, in which there is mag- 
 netism, is called a magnetic field. The magnetic field ^ 
 strongest near the poles. The magnetic field may be 
 drawn in the following way: 
 
 Experiment 74. To Draw a Magnetic Field. 
 Apparatus: Bar magnet, iron filings in salt sifter. 
 
 Materials: Piece of paper. 
 
 a. Lay the magnet upon a table, cover it with the 
 piece of paper, and slowly sift the iron filings upon the 
 paper. They will take certain positions and they may be 
 aided in arranging themselves by jarring the table a little. 
 Draw with a soft pencil a large number of lines, following 
 as closely as possible the lines which the filings are 
 taking. After drawing the lines return the filings to the 
 sifter. 
 
 b. Hide the drawing and make another drawing 
 from memory. Then compare your two drawings and 
 see what you have omitted. You should learn to draw a 
 magnetic field from memory. 
 
MAGNETIC FIELDS 
 
 177 
 
 Just as you 
 made blue 
 prints of leaves 
 and small ob- 
 jects, and cop- 
 i e d drawings, 
 so you can ob- 
 tain blue prints 
 o f magnetic 
 fields. The il- 
 lustration gives 
 one example of 
 a magnetic field. You can make many. 
 
 Experiment 75. Blue Prints of Magnetic Fields. 
 
 Apparatus: Two bar magnets, piece of window 
 glass, iron filings in a salt shaker. 
 
 Materials: Blue-print paper. 
 
 a. Lay the two magnets upon a book, side by side, 
 about the width of the magnets apart, having the two 
 north poles pointing in the same direction. Lay a piece 
 of blue-print paper upon the magnets with the yellow side 
 up. Keeping in the shade, sprinkle iron filings upon the 
 paper as in the last experiment. When the filings are 
 nicely arranged cover them carefully with the piece of 
 window glass, and place in the bright sunlight. When 
 the paper has changed to the familiar bronze, return the 
 filings to the shaker and immediately wash the blue print 
 in water. 
 
 b. Repeat (a) above, but have the north pole of one 
 magnet and the south pole of the other magnet pointing 
 the same way. After the blue-print is made compare it 
 
 Elem. Sci. 12 
 
178 
 
 MAGNETISM AND ELECTRICITY 
 
 with the other blue print. Notice that the lines of force, 
 as the filing are said to indicate, seem to push against 
 one another in (a) and pull upon one another in (b). 
 
 So far we have noticed that magnets attract iron. 
 Now we are going to learn about the effect which two 
 magnets have upon each other. 
 
 Experiment 76. Attraction and Repulsion. 
 Apparatus: Two bar magnets, stand. 
 Materials : Thread, heavy paper, 
 a. Make a support for one magnet from the paper 
 
 and hang it up by 
 the thread, as shown 
 i n the illustration. 
 The thread will un- 
 twist but the magnet 
 will finally come to 
 rest. Then bring up 
 one pole of the other 
 magnet to one pole of 
 the supported mag- 
 net. What happens? 
 The magnets have 
 their north poles marked. Which poles caused the 
 result? Now bring the other pole to the same pole of 
 the supported magnet and tell what happens. As we 
 have learned, if the poles come together it shows attrac- 
 tion ; if they go away from each other we call it repul- 
 sion. What is the rule for attraction and repulsion? 
 
INDUCED MAGNETISM 179 
 
 The illustration shows an experiment which you 
 should repeat for yourself. 
 Take a nail and hold it near a 
 magnet but not touching it. 
 The nail will then attract iron 
 filings. Remove the magnet 
 and the nail loses its magnet- 
 ism. Magnetism which is 
 caused in this manner is called 
 induced magnetism. Magnet- 
 ism must be induced in an object before it can be 
 attracted by a magnet. Since iron is the only common 
 material which can have magnetism induced in it, it is 
 the only common metal which can be attracted. Steel 
 is made from iron and retains its magnetism better than 
 iron because it is harder. Electricity can produce in 
 iron much stronger magnetism than can exist in steel 
 magnets. We shall learn about this next year. 
 
 Review Questions, 28. 
 
 1. What are the advantages of sunlight? 
 
 2. What is the proper method of heating water, 
 from above or from below? Explain. 
 
 3. How do fishes live in the water? Do plants help 
 fishes? Do plants help man? Explain fully. 
 
 4. Why do we eat? Why do w r e drink? When do 
 we need to eat fat? When do we need to drink a large 
 amount of water? 
 
 5. Name some plants which are harmful to man. 
 What can we do to prevent these plants from harming 
 us? 
 
180 ELECTRICITY AND MAGNETISM 
 
 6. Name all the advantages of tilling the soil and 
 tell how tilling may be accomplished. 
 
 7. What is a machine? Of what use is a machine 
 to us? Name two simple machines and explain how they 
 help us. 
 
 What are magnets? What are the two kinds of 
 magnets? What is meant by attraction? 
 
 9. What are the poles of a magnet? How are the 
 poles of a magnet different from the rest of the magnet? 
 What are lines of force? 
 
 10. What is a keeper and what is its use? What 
 is a magnetic field? W T hat is meant by repulsion? What 
 is induced magnetism? 
 
THE GUIDE 
 
*THE ARTS AND INDUSTRIES. 
 
 69. Weather Observations. 
 
 The observation of the weather is valuable for many 
 reasons. If we make observations regularly we get into 
 the habit of keeping records of the observations in order 
 to compare them with later ones. We soon learn that 
 our memory is often weak and that records are to be 
 trusted every time. The value of the records grows as 
 they increase. Thus a record of the daily temperature 
 for two years is much more valuable than for one year, 
 while a record for ten years is of great value, especially 
 in a farming district. Why? In the same way the rec- 
 old of the rainfall for several years helps the farmers, for 
 they would not plant crops which require a very large 
 amount of water in a locality where the rainfall is always 
 small. 
 
 The records which you are beginning to keep will 
 become a source of great pleasure to you as you grad- 
 ually add more observations, and the record for each 
 kind of observation increases with time. Begin by 
 
 * Note to the Teacher: The scientific facts, upon which 
 the following practical applications are based, have been stud- 
 ied in the preceding divisions. The great purpose of this 
 division is to show that science is a matter of everyday interest 
 and is of immense value to everyone alike. Since the prin- 
 ciples have been stated in other sections these sections are 
 necessarily shorter than those others. 
 
MOW TO MAKE BLUE-PRINT PAPER 183 
 
 arranging your records in orderly columns. As time 
 goes on, the arrangement in columns permits an easy 
 reference to past observations, and all the records of the 
 same kind are together. The government of the United 
 States is continually making records of the weather and 
 these observations save millions of dollars every year to 
 farmers and ship owners. 
 
 70. How to Make Blue-Print Paper. 
 While blue-print paper may be purchased at a small 
 price, it is often desirable to prepare certain kinds of 
 paper so that prints may be made on them. Another 
 use of the mixture is to apply it to cloth. Simple cotton 
 cloth soaked in it may be printed upon in the same man- 
 ner as upon paper. A collection of prints of leaves may 
 be made and the different pieces .may then be sewed 
 together to form a pillow cover. The solutions should be 
 made as follows: 
 
 Solution A. Distilled water 125 cubic centimeters.* 
 Potassium Ferricyanide 25 grams. 
 Gum Arabic 2 grams. 
 
 Solution B. Distilled water 125 cubic centimeters. 
 Iron ammonia citrate 37 grams. 
 Gum Arabic 2 grams. 
 
 Use equal parts of A and B, mixing them only in the 
 dark. Candle light may be used. The two solutions are 
 not affected by light until they are mixed. Paper which 
 has no coating upon it should be used. The mixture may 
 be applied in two ways it may be poured upon the paper 
 
 * See Sections 58 and 59 for information in regard *o 
 measuring and weighing. 
 
184 THE ARTS AND INDUSTRIES 
 
 and the excess allowed to drip off, or it may be applied 
 by means of a swab of cotton upon a little stick. The 
 paper must be allowed to dry in the dark before being 
 used. It is best not to prepare any more paper than will 
 be used within a few days, as it spoils quite quickly. 
 
 It is not necessary to cover- the whole of a piece of 
 paper if the print is to be a small one upon a large sheet 
 of paper. Merely apply the mixture where it is needed. 
 
 71. Solar Heaters. 
 
 In Experiment 22 it was noticed that black and rough 
 materials become much warmer in the sun than do other 
 objects. Man has made use pf this knowledge by making 
 the sun warm water for him. If many feet of water pipe 
 are painted black and exposed to the heat of the sun 
 the water within them will become quite hot. This is 
 a simple solar heater. The longer the pipe the more 
 water can be heated at one time. Man has learned 
 something else about the heat from the sun. If a box is 
 made of wood, painted black inside, and covered with 
 glass, the heat which is received from the sun can enter 
 the box but cannot get out again as rapidly. Thus the 
 temperature inside the box rises much higher than the 
 temperature outside, if the sun is shining. Now if such 
 a box is filled with many feet of water pipe, the water 
 which is inside the pipe will become very hot. Such a 
 heater on a sunny day can raise the temperature of water 
 hieh enough for a hot bath. The water from a solar 
 
 J> o 
 
 heater does not have to be heated very much in order to 
 make it boil, so for cooking purposes it causes a saving 
 in fuel. 
 
HOT-AIR ENGINE FIREPROOFING 
 
 185 
 
 A.r 
 
 72. Hot-Air Engines. 
 
 If air is heated it expands, as was learned in Section 
 18. This principle has been used to obtain 
 power. The illustration shows a very sim- j 
 pie hot-air engine. If a tube is closed at 
 one end and has the other end sliding, which 
 is called a piston, when the air inside is 
 strongly heated by a Bunsen burner it. will 
 expand and force the piston out. After re- 
 moving the burner the air will cool and con- 
 tract and the piston will return to its first 
 position. This is the principle of the hot- 
 air engine but the usual engine has many 
 more parts, and the hot air is exchanged for cold air 
 instead of waiting for the hot air to become cold. You 
 know now why the engine works. To learn just how it 
 works will require further study after you have had more 
 about machines. 
 
 73. Fireproofing. 
 
 Some materials burn much more easily than others 
 and the same kind of material burns more easily if il is 
 opened up to the effect of the air than if it is tightly rolled 
 or compressed. The reason for this is, that if a body is 
 porous the oxygen of the air can get at more of the mate- 
 rial at one time and more burning or combustion can take 
 place. Since this is so, if we wish to make some mate- 
 rial less easy to burn we must put something upon it 
 which will keep away the air from its surface. A solu- 
 tion which contains tin, or a solution of water glass, will 
 accomplish this purpose quite well without harming the 
 material. 
 
186 THE ARTS AND INDUSTRIES 
 
 It must be remembered, however, that nothing which 
 can burn can be made really fireproof. If the temper- 
 ature is raised high enough the material will burn or be 
 destroyed, no matter what is upon it. Fireproofing 
 serves to prevent easy burning and on that account is a 
 very valuable process. 
 
 74. Waterproofing. 
 
 Many substances are more or less porous and allow 
 water to penetrate them. As we learned in Experiment 
 46, water may be kept out of material by stopping the 
 pores. In that experiment paraffin was used but there 
 are other somewhat similar materials which may be used 
 in the same manner. Thus if the pores of cloth are filled 
 with rubber we obtain what we call rubber cloth. Oil- 
 cloth and oilskins are other examples of the filling of 
 pores of cloth. The foundations and cellar floors of 
 buildings may be made waterproof by covering them 
 with melted tar, or tar paint; by asphalt, and by the 
 addition of other matter to the concrete before it is 
 mixed. 
 
 Another very interesting method is to have the pores, 
 but treat the cloth in such a way that water will not read- 
 ily enter. The following experiment shows the prin- 
 ciple which underlies this method. 
 
 Experiment 77. Waterproofing. 
 
 Apparatus: Burner, ring stand, wire gauze, tin 
 dish, small glass tube, glass. 
 
 Material: Paraffin. 
 
 a. Insert the glass tube in some water in the glass 
 and note how high the water goes by capillarity. See 
 Section 41. 
 
WATERPROOFING 187 
 
 b. Melt some paraffin by gentle heat and dip the 
 tube into it. Warm 'the tube gently until the paraffin is 
 spread in an invisible layer up inside it, without stopping 
 the hole. This makes the hole smaller and you might 
 expect that the water would go higher in it. When the 
 tube is cold place it in the water. Where is the surface 
 of the water inside the tube? 
 
 This is the principle by which raincoats keep out the 
 rain. The goods are porous but there has been produced 
 a change in the threads so that capillarity has been de- 
 stroyed. It is impossible to wet anything beneath the 
 surface unless capillarity acts. Why do you wet a mop 
 before using it? 
 
 75. Flavoring Extracts and Perfumes. 
 
 The making of flavoring extracts and perfumes are 
 examples of solution by special solvents. In this case 
 alcohol is the solvent. Vanilla extract may be made by 
 grinding vanilla beans in a meat chopper and allowing 
 the mass to soak in a mixture of one-half pure alcohol 
 and one-half distilled water, in a stoppered bottle for 
 several days. A small amount of sugar may aid the 
 solution. This will produce a delicately flavored extract 
 at a moderate price. 
 
 Grate off the outside of several lemons, or oranges, 
 and soak the gratings for several days in pure, undiluted 
 alcohol if you wish to make lemon or orange flavoring 
 extracts at a slight price. 
 
 Many perfumes may be made by allowing the mate- 
 rial, whose perfume is desired, to soak for several days in 
 
188 THE ARTS AND INDUSTRIES 
 
 pure undiluted alcohol. All of these solutions must be 
 kept in tightly covered bottles as the alcohol will rapidly 
 evaporate if the bottles are left unstoppered. 
 
 76. To Remove Grease Spots and Stains. 
 
 We may make use of both solution and capillarity 
 for the removal of grease. In addition to the solvents 
 which are mentioned in Section 36 there are ammonia 
 water, naphtha, benzine, and ether for the removal of 
 grease. All but ammonia water are very dangerous to 
 use as they are so easily set on fire. Grease can also be 
 removed by means of a hot iron. Place a cloth or blot- 
 ting paper under the goods, cover the goods with a cloth 
 or a piece of paper, and press with a moderately hot iron. 
 The heat melts the grease and weakens the capillarity so 
 that the grease moves away from the heat. 
 
 Ink spots may be removed by salt and lemon juice 
 if the spots have not become dry. Red ink may be 
 removed by ammonia water. Paint may be removed by 
 turpentine and benzine. Tea and coffee stains may be 
 removed by cold water and glycerine if allowed to soak 
 for several hours. Enameled sinks and bathtubs may be 
 cleaned with kerosene, followed by hot water and soap. 
 
 77. How to Make Soap. 
 
 There are two kinds of soap hard and soft. In 
 olden days, before soap became so common and so cheap, 
 soapmaking was one of the household arts. Then there 
 was much soft soap made as it was easily made and con- 
 venient to use. Now hard soaps of various kinds have 
 nearly driven this art from the home. 
 
SOAP MAKING 189 
 
 Soap is a combination of grease and lye. Caustic 
 potash and grease make soft soap, while caustic soda and 
 grease make hard soap. The kind of grease which is 
 used makes the soap high grade or low grade ; toilet soap 
 or laundry soap. 
 
 Experiment 78. Soap Making. 
 Apparatus: Burner, ring stand, tin can. 
 
 Materials: Lard, sodium hydroxide (caustic soda), 
 salt. 
 
 To 85 cubic centimeters of water in the tin can add 
 15 grams of sodium hydroxide and 40 grams of lard ; boil 
 slowly ten minutes. Be very careful that the mixture 
 does not spatter upon you. After boiling add about 25 
 grams of salt and continue to boil for five minutes. Then 
 allow all to cool and remove the soap which will be on 
 top. Let the cake dry for several days, and then see if 
 it will produce suds. 
 
 78. Bread Making. 
 
 There are several kinds of bread but they can all be 
 placed in two classes bread raised by baking soda and 
 bread raised by yeast. In all cases the bubbles are 
 formed by carbon dioxide. In Experiment 48, (d), we 
 saw that baking soda and cream of tartar, when mixed in 
 solution, produce carbon dioxide. The cream of tartar 
 should be mixed dry with the flour, and the baking soda 
 dissolved in a little water, if they are to accomplish the 
 most good. Why? In Experiment 63 it was shown 
 that baking soda, when added to sour milk, makes it 
 sweet. At the same time carbon dioxide is produced by 
 the action of the acid in. the milk upon the baking- soda. 
 
190 THE ARTS AND INDUSTRIES 
 
 This explains why sour milk can be used with soda for 
 pancakes or griddle cakes. Should the baking soda be 
 added to the milk or should it be dissolved in a little water 
 and added to the mixture after the sour milk has been 
 stirred in? Explain. 
 
 When bread is made yeast is added to make it "rise." 
 The yeast uses the sugar which is added to the mixture, 
 and some of the flour is changed to a kind of sugar which 
 the yeasts can use. Carbon dioxide is produced which 
 forms the bubbles and thus the dough swells and becomes 
 porous and tender. Most of the alcohol bakes out. Why 
 is bread made with warm water during the cold weather? 
 Another use for yeast is in the making of homemade 
 root beer. The stopples "pop" when the bottles are 
 opened on account of the large amount of carbon dioxide 
 which the liquid contains. 
 
 79. Alcohol for Industrial Purposes. 
 
 Alcohol may be made from any vegetables or stalks 
 of crops, which contain starch or sugar, by means of 
 yeast. This means that much of the waste in crops due 
 to small vegetables or some damage which renders the 
 vegetables unfit for sale may be turned into alcohol 
 which is very valuable for many of the arts and indus- 
 tries. Alcohol is used in large quantities as a solvent, 
 and it is also used for lighting, heating, cooking, and 
 for running engines. 
 
 The United States Government has removed the tax 
 on alcohol if it is not to be used as a drug or drink. The 
 only requirement is that something must be added to the 
 alcohol which will render it unfit for persons. Alcohol 
 in this condition is called denatured. 
 
ALCOHOL FOR INDUSTRIAL PURPUOSES 
 
 191 
 
 Experiment 79. Making and Distilling Alcohol. 
 Apparatus: Burner, ring stand, wire gauze, flask, 
 tin grater, glass tube, test tube, glass. 
 
 Materials: Molasses, potatoes, yeast. 
 
 a. Experiment 62 may be repeated and the fer- 
 mentation allowed to continue 
 
 for three days. Then arrange 
 apparatus as shown in the il- 
 lustration and warm the mixture 
 very gently. Alcohol will pass 
 off just before the boiling tem- 
 perature of the water is reached 
 and will collect in the tube which 
 is placed in the cold water. The 
 alcohol should b ur n when 
 poured upon a plate and touched 
 with a match. 
 
 b. Grate some raw potatoes, mix with water, and 
 add about one-tenth as much yeast as there is mash 
 Allow to ferment as in (a) above, and distil. 
 
 80. The Pantagraph. 
 
 The pantagraph, as shown in the illustration is a 
 
 ______ . -^My.: r>~ 
 
192 THE ARTS AND INDUSTRIES 
 
 practical application of the lever, and is used to enlarge 
 drawings or to make them smaller. It is made from four 
 long, thin sticks which have holes, at regular intervals, 
 in which pegs may be inserted. The block on the right 
 hand lower corner is fixed to the table. All the rest of 
 the pantagraph is free to move. The point under 
 the hand does not mark ; the point over the smaller pic- 
 ture is a pencil. The little wheel at the left of the 
 pantagraph is not necessary but allows it to move more 
 freely. By moving the point over all the lines in a 
 drawing an exact copy is made by the pencil only the 
 new drawing is smaller in this case. To enlarge a draw- 
 ing the non-marking point is placed where the smaller 
 picture is, and the pencil is placed where the hand in the 
 picture now is. 
 
 When studying the lever you learned that the small 
 force moves a longer distance than the large force. The 
 pantagraph may be considered as four levers all acting 
 together. A certain motion of one part will make a 
 larger or smaller motion of another part according as 
 the lengths of the arm are changed by changing the pegs. 
 Make a pantagraph and copy some drawings. 
 
 81. Levelling. 
 
 It is very often desirable to know how to make level 
 the foundations of a building. The illustration shows a 
 very simple method which has been used for many years. 
 The apparatus is made of the size as shown. The plumb- 
 bob hangs from (b), and the plumb-line is kept from 
 swinging too much by some wide staples. To adjust 
 the apparatus rest the two ends upon two stakes driven 
 
LEVELLING 
 
 193 
 
 into the ground, driving in the high stake until the 
 plumb-line is about in, the middle of the board (bd). 
 Then mark just where the point of the plumb bob comes 
 Reverse the apparatus upon the stakes, without chang- 
 ing them and mark where the point of the plumb-bob 
 comes. Exactly halfway between the two marks is the 
 proper place to put the level mark. When the apparatus 
 is placed so that the plumb-bob comes to this mark the 
 bottom stick is level. 
 
 Sometimes a certain slant is wanted, as when ditches 
 are being dug to carry water. In this case a block is 
 placed at (ce), having a length according to whatever 
 drop, as it is called, is wanted for each eleven feet. Then 
 the apparatus is used as in levelling, but instead of being 
 level the ground has the slant which is desired. 
 
 Cut supplied through United States Department of Agriculture. 
 
 Elern. Sci. 13 
 
ire GUIDE 
 
APPENDIX. 
 
 REFERENCE BOOKS ON BIRDS. 
 
 Farmers' Bulletins: 
 
 No. 54. Some Common Birds. 
 No. 493. The English Sparrow as a Pest. 
 No. 506. Food of Some Well-known Birds. 
 No. 513. Fifty Common Birds of Farm and 
 Orchard. 
 
 Finley, W. L., American Birds, Scribners. 
 National Geographic Magazine, June, 1913. 
 
 REFERENCE BOOKS ON FLOWERS. 
 Farmers' Bulletins : 
 
 No. 28. Weeds ; and How to Kill Them. 
 No. 86. Thirty Poisonous Plants. 
 No. 188. Weeds Used in Medicine. 
 No. 195. Annual Flowering Plants. 
 
 Going, M., Field, Forest, and Wayside Flowers, 
 Baker and Taylor Co. 
 
 REFERENCE BOOKS ON TREES. 
 
 Farmers' Bulletins: 
 
 No. 134. Tree Planting on Rural School Grounds. 
 No. 173. Primer of Forestry. Part 1. 
 No. 358. Primer of Forestry. Part 2. 
 No. 423. Forest Nurseries for Schools. 
 
 Mathews, F. S.. Familiar Trees, Appletons. 
 
LIST OF APPARATUS AND MATERIALS. 
 
 The numbers indicate the first experiments in which 
 the apparatus or the material is used. The amount 
 needed will depend upon the number of pupils but, as 
 will be seen, the expense will be slight. 
 
 1. Sticks, 3'x^"x^". 16. 
 String. 17. 
 
 2. Rules, 12" 30cm. 
 Scissors. 
 Dividers. 
 
 Cardboard. 18. 
 
 Paper rivets. 19. 
 
 Pins. 
 
 3. Nails, assorted. 
 Odd pieces of board. 
 
 5. Protractors. 
 
 Hatpins. 
 8. Bottles, assorted. 
 
 Files, triangular. 
 
 Cork stoppers. 
 
 Glass tubing, J4". 
 
 Sand. 20. 
 
 10. Thumb tacks. 
 Chalk boxes. 
 
 11. Window glass. 22. 
 Candles. 
 
 12. Knives. 23. 
 
 13. Colored cloth, as- 
 
 sorted. 24. 
 
 14. Blue-print paper. 
 
 Library paste. 
 Mirrors, 2"x4". 
 Rubber bands. 
 Block of wood. 
 
 2"x2"x4". 
 Drinking glasses. 
 Kerosene lamp. 
 Kerosene. 
 Bunsen burners. 
 Alcohol lamps. 
 Alcohol. 
 Test tubes, 6"x24" ; 
 
 8"xl". 
 
 Test-tube holders. 
 Iron Wire, No. 28. 
 Soft coal. 
 Some article with 
 
 luminous paint on 
 
 it. 
 
 Spice cans. 
 Paper, asorted colors. 
 Glass lenses,3" diam. 
 Iron wire No. 18. 
 Argand or student 
 
 lamp chimneys. 
 
LIST OF APPARATUS 
 
 25. Unequal expansion 
 
 apparatus. 
 Salt. 
 
 26. Cheap thermometers. 
 
 27. Ring stands with 
 
 three rings. 
 Wire gauze, 5"x5". 
 
 27. Circular tin cans, as- 
 
 sorted. 
 
 28. Blocks of wood, 
 
 2"x4"x6". 
 Wooden rods, 7" 
 
 long, 1" diam. 
 Lubricating oil. 
 
 29. Friction gaslighters. 
 
 30. Turpentine. 
 
 Pieces of broken 
 chinaware. 
 
 31. Charcoal. 
 
 Pieces o f various 
 combustibles. 
 
 33. Baking soda. 
 Bandages. 
 Limewater. 
 Olive oil. 
 
 34. Copper rods, No. 12, 
 
 6" long. 
 
 Iron rods, No. 12, 6 
 long. 
 
 37. Wing tops for Bun 
 
 sen burners. 
 
 38. Saucers o r shallow 
 
 dishes. 
 
 AND MATERIALS 197 
 
 39. One 20-oz. bottle. 
 Medicine droppers. 
 Phenolphthalein, 
 
 KOZ. 
 
 40. Potassium chlorate. 
 Manganese dioxide. 
 
 41. Glass funnels. 
 Syringe bulbs. 
 Glass jar, 6"x8". 
 
 Rubber tubing. 
 3-16" hole. 
 
 42. Gallon bottle. 
 Large pan to hold 
 
 two gallons. 
 
 43. Pie tins. 
 
 Small round bottles 
 
 with stoppers. 
 Levels, ($.20). 
 
 45. Balances, (can be 
 
 made). 
 
 Set of weights, 500 g. 
 Sponges. 
 - Stones. 
 Pieces of bricks. 
 
 46. Paraffin. 
 
 47. Filter paper, 5". 
 Sawdust. 
 
 48. Tin spoons. 
 Sugar. 
 
 Cream of tartar. 
 Ammonium chloride. 
 
198 
 
 APPENDIX 
 
 49. Gasolene. 
 Lard. 
 Rosin. 
 
 Pitch, or some tree 
 gum. 
 
 50. Beakers, 200 cc. 
 Alum. 
 
 Copper suphate. 
 
 51. Powdered or shaved 
 
 soap. 
 
 52. Beans. 
 
 53. Very small glass 
 
 tubing, assorted. 
 Lamp wicks. 
 Red ink. 
 Cube sugar. 
 
 54. Cake pans. 
 Gravel. 
 Loam. 
 Cheese cloth. 
 
 56. Blotting paper. 
 Seeds of beet, corn, 
 
 pea, etc. 
 
 57. Wooden tray, 
 
 12"xl2"x2". 
 
 58. Large pickle bottles. 
 Black cloth. 
 
 59. Paper in sheets 
 
 17"xll". 
 
 60. Labels. 
 
 61. Seeds of apple, pear, 
 
 orange, lemon. 
 
 62. Molasses. 
 Yeast. 
 
 63. Powdered borax. 
 Absorbent cotton. 
 
 64. Graduate, 50 cc. 
 
 65. Materials etc. for bal- 
 
 ance. 
 69. Spring balances, 
 
 250g. 8 oz. 
 Window roller 
 
 springs. 
 
 71. Triangular pieces of 
 
 wood. 
 
 72. Little car for inclined 
 
 plane. 
 
 73. Lodestone. 
 Bar magnets. 
 Horseshoe magnets. 
 
 74. Pepper boxes. 
 Iron filings. 
 
 Section 70. 
 
 Potassium ferricyan- 
 
 ide, 1 oz. 
 Iron-ammonia citrate 
 
 iy 2 oz. 
 Gum Arabic, % oz. 
 
 78. Sodium hydroxide. 
 
 79. Tin vegetable grater. 
 Potatoes. 
 
OTHER BOOKS BY THE SAME AUTHOR 
 
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