Construction and use 40 65. Hygrometers 40 Psychrographs 66. The Draper psychrograph 41 67. Placing the instrument 42 68. Regulating and operating the instrument 43 69. The weekly visit 44 Humidity Readings and Records 70. The time of readings 44 71. Place and height 45 72. Check instruments 45 73. Humidity tables 46 74. Sums, means, and curves 47 Conversion scale for temperatures 75. Records 48 Light 76. Methods 48 The Photometer 77. Construction 49 78. Filling the photometer 50 79. Making readings 50 80. The Dawson-Lander sun recorder 51 81. The selagraph 52 Standards 82. Use 53 83. Making a standard 53 84. Kinds of standards 54 Readings 85. Time 55 Chart for determining sun’s altitude 57 86. Table for determining apparent noon 58 87. Place 59 Table of intensity at various angles 60 Reflected and Absorbed Light 88. The fate of incident light 60 89. Methods of determination 61 90. Leaf and epidermis prints 62 Expression of Results 91. Light records 63 92. Light sums, means and curves 63 Temperature 93. 64 Thermometers 94. Air thermometers 64 95. Soil thermometers 64 96. Maximum-minimum thermometers 65 97. Radiation thermometers 67 98. Thermographs 67 Readings 99.