CONTENTS. IX 



141. Vapor pressures of methyl alcohol . 149 



142. " " and temperatures: (a) carbon disulphide . . . 150 



() chlorobenzine . . . 150 

 (*r) bromobenzine . . . 150 



(d) aniline 150 



(e) methyl salicylate . . . 151 

 (/) bromonaphthaline . . 151 

 () mercury . . . .151 



143. Vapor pressure of solutions of salts in water 152 



144. Pressure of saturated aqueous vapor at low temperature over ice . 154 



145. " " " " " " " " " water . 154 



146. " " " " " oto5oC . . . .154 

 147- " " " " " 50 to 374 C . .155 



148. Weight in grains of aqueous vapor in a cubic foot of saturated air .156 



149. " " grams " " " " " " meter of " " . 156 



150. Hygrometry, vapor pressure in the atmosphere 157 



151. dew-points . . . . . . . . . 158 



152. Relative humidity .......... 160 



153. Values of 0.378*? in the atmospheric pressure equation /* = .Z? 0.378*? 161 



154. Table for facilitating the calculation of ^760 162 



155. Logarithms of 6/760 for values of h between 80 and 800 . . . 162 



156. Values of i+ 0.00367 /: 



(a) for values of t between o and 10 C, by tenths . . .164 



(b) " " " " " - 90 " + 1990 C, by tens . . 165 



(c) Logarithms for t "49 " +399 C, by units . . 166 

 (/) " " " " 400 1990 C, by tens . . .168 



157. Determination of heights by the barometer 169 



158. Barometric pressures corresponding to different temperatures of the 



boiling-point of water : 



(a) Common measure . . . . . . . .170 



(b) Metric measure . . . . . . . . -171 



159. International Primary wave-length standard, Red Cd. line . . . 172 



1 60. Secondary " standards Fe. arc lines . . .172 



161. Additional standard Fe. lines 172 



162. Stronger lines of some of the elements 172 



163. Rowland's standard solar wave-lengths (also corrections) . . .173 



164. Tertiary standard wave-lengths Fe. arc lines 176 



165. Wave-lengths of the Fraunhofer lines 177 



1 66. Photometric standards 178 



167. Intrinsic brightness of various lights 178 



1 68. Visibility of white lights 178 



169. Efficiency of various electric lights . . . . . . . 179 



170. Sensitiveness of the eye to radiation of different wave-lengths: low 



(threshold) intensities . . . . . . . . . 180 



171. Sensitiveness of the eye : greater intensities 180 



172. Sensibility of the eye to small differences of intensity (Fechner) . 180 



