Vlii CONTENTS. 



I 



97. Terrestrial magnetism: total intensity 115 



98. " secular change of total intensity . . . 115 



99. agonic line . . . . . . .116 



100. Magnetic elements at magnetic observatories . . . . -117 



101. Pressure of mercury and water columns 118 



102. Reduction of barometer to standard temperature . . . .119 



103. " " gravity, inch and metric scales . 120 



104. " " " " latitude 45 : inch scale . . . .121 



105. " " " " " " metric scale . . .122 



106. Correction of barometer for capillarity : inch and metric scale . . 123 



107. Volume of mercury meniscus in cu. mm. . . . . . .123 



108. Aerodynamics: data for wind pressures . . . . .124 



109. " " the soaring of planes ..... 125 



no. Coefficients of friction 126 



in. Lubricants 126 



112. " for cutting tools 126 



113. a Viscosity of water at different temperatures ..... 127 

 b Specific viscosity of water at different temperatures . . .127 



114. Coefficients of viscosity for solutions of alcohol in water . . . 128 



115. Specific viscosity of mineral oils 128 



116. " various oils . . . . . . . 128 



117. Viscosity of various liquids 129 



118. " " " " temperature variation .... 130 



119. Specific viscosity of solutions : variation with density and temperature 131 



120. " " " " atomic concentrations . . . 135 



121. Viscosity of gases and vapors 136 



122. " " air 20? 2 C 136 



123. " gases and vapors, temperature variation . . . -137 



124. Diffusion of an aqueous solution into pure water .... 138 



125. " vapors . . 139 



126. " " gases and vapors ........ 140 



127. " " metals into metals . 140 



128. Solubility of inorganic salts in water : temperature variation . . 141 



129. " a few organic salts in water : temperature variation . 142 



130. " gases in water . . . , . . . . 142 



131. " , change produced by uniform pressure .... 143 



132. Absorption of gases by liquids 144 



133. Capillarity and surface tension : water and alcohol in air . . . 145 



134. miscellaneous liquids in air . -145 



135. aqueous solutions of salts . . . 145 



136. Capillarity and surface tension : liquids in contact with air, water or 



mercury . . . . . . . . . . . . 1 46 



137. Capillarity and surface tension : liquids at solidifying point . 146 



138. " " " " thickness of soap films . . .146 



139. Vapor pressures . . 147 



140. " " of ethyl alcohol . . . . . . -149 



