1G 



NUMBERS AND MEASURES. 



(18) COMPARATIVE VELOCITIES IN METRES PER SECOND. 



Neptune round sun ... 5390 



Sun to wards Hercules... 7642 



Jupiter round sun 12924 



Mars round sun 23863 



Earth round sun 29516 



Venus round sun 34630 



Mercury round sun 47327 



Solar atmosphere or- 

 dinary 30000 



Solar atmosphere up to 65000 

 Halley's comet in peri- 

 helion 393260 



Tempests in solar at- 

 mosphere 402000 



Electricity in a sub- 

 marine wire 4000000 



Electricity in an aerial 



wire...f 36000000 



Light 300400000 



Earthquake concussion 



(July '55) 1363 



(19) COMPRESSIBILITY OF SOLIDS AND LIQUIDS. 



The coefficient of volume-elasticity is the quotient of the pressure 

 in tonnes (1000000 grams) per square centimetre by the compres- 

 sion, i.e. by the ratio of the change in volume to the original 

 volume. 



Water 15 C. 



Alcohol .... 15 C. 



Ether 14 C. 



Carbon disulphidc... 14 C. 

 Mercury 15 C. 



22-63 

 11-4 

 8-07 

 16-3 

 552-5 



Glass 423 



Steel 1876 



Iron 1485 



Copper 1717 



Brass (mean) 1063 



(20) RIGIDITY. 



The "modulus of rigidity" of a square bar is the amount of 

 ^tangential stress in tonnes per square centimetre divided by the 



