CONTENTS 



Vll 



57. 



Records and Results 

 55. The field record 



The permanent record 

 Sums and means 



58. Curves 

 Humidity 



59. Instruments 

 Psychrometers 



60. Kinds 



61. The sling psychrometer 



62. Readings 



63. Cog psychrometer 



64. Construction and use 



65. Hygrometers 

 Psychrographs 



66. The Draper psychrograph 



67. Placing the instrument 



68. Regulating and operating the instrument 



69. The weekly visit 

 Humidity Readings and Records 



70. The time of readings 



71. Place and height 

 y2. Check instruments 

 y^i- Humidity tables 



Sums, means, and curves 



Conversion scale for temperatures 

 Records 



74. 



75- 



L^isht 



']6. Methods 

 The Photometer 



77- 

 78. 



79- 

 80. 



Construction 



Filling the photometer 



Making readings 



The Dawson-Lander sun recorder 



81. The selagraph 

 Standards 



82. Use . 



83. Making a standard 



84. Kinds of standards 

 Readings 



85. Time 



Chart for determining sun's altitude 



