CONTENTS. Vll 



470. Variation of the moduli of rigidity with the temperature . . . 74 



48. Young's modulus .......... 75 



49. Compressibility of the more important solid elements . . . -76 



50. Hardness ............ 76 



51. Relative hardness of the elements 76 



52. Poisson's ratio . . . . . . . . . . 76 



53. Elastic moduli of crystals, formulae 77 



54. " " " " numerical results 78 



55. Compressibility of O, air, N, H at different pressures and temperatures 79 



56. " " ethylene " " " " " . 79 



- it n it (6 it j~ 



58. " " carbon dioxide at " " " " . 80 



59. " gases, values of a . . . . . . .80 



60. " " air and oxygen between 18 and 22C . . .80 



61. Relation between pressure, temperature and volume of sulphur dioxide 81 



62. " " " " " " " ammonia . 81 



63. Compressibility of liquids 82 



64. " " " 83 



65. Specific gravities corresponding to the Beaume' scale . . . .84 



66. Densities of the solid and liquid elements 85 



67. " various woods . 87 



68. " " " solids 88 



69. " " " alloys 89 



70. " " " liquids 90 



71. " " " gases 91 



72. " " " aqueous solutions of salts, bases and acids . . 92 



73. Density of water between o and 36 C ...... 94 



74. Volume of water at temperatures between o and 36 C in terms of its 



volume at the temperature of maximum density . . . -95 



75. Density and volume of water at different temperatures from -10 to 25oC 96 



76. " " " " mercury at " " " -10 " 36oC 97 



77. Specific gravity of aqueous ethyl alcohol ...... 98 



78. Density of aqueous methyl alcohol ....... 99 



79. Variation of the density of alcohol with the temperature . . .100 



80. Velocity of sound in solids ......... 101 



8 1. " " " " liquids and gases 102 



82. Musical scales 103 



83. " " 103 



84. Force of gravity at sea level and different latitudes . . . .104 



85. Results of some of the more recent gravity determinations . . . 105 



86. Value of gravity at some of the U. S. C. and G. Survey stations . .106 



87. Length of seconds pendulum for sea level and different latitudes . 107 



88. Determinations of the length of the seconds pendulum . . . 107 



89. Miscellaneous data as to the earth and planets . . . . .108 



90. Terrestrial magnetism : secular change of declination . . .no 



91. " " dip or inclination 112 



92. " secular change of dip 112 



93. " " horizontal intensity 113 



