SCIENCE OF COMMON THINGS. 135 



Extremes of temperature. Melting point of iron. Greatest artificial heat. 



3S-6 below zero. 



850 At what temperature does fresh water freeze? 



At 32 above zero. 



851 At what temperature does salt or sea water freeze f 



At 28 '5 above zero. 



85S Why does it require a greater amount of cold to cause sea water to 

 congeal, than it does fresh water f 



Because sea water contains salt and other substances 

 which tend to prevent congelation. 



853 What is the average temperature at the equator 1 



In America, 81'5 ; in Africa^ 83. 



854 What is blood-heat, or the vital temperature of the human body t 



98. 



855 At what temperature does alcohol boil f 



Under the ordinary atmospheric pressure at 1T3*5. 



856 At what temperature does water boil T 



Under the ordinary atmospheric pressure at 212. 



85*7 At what temperature does lead melt ? 



At 594. 



858 At what heat does mercury boilf 



At 661 under the common atmospheric pressure. 



859 At ivhat temperature do brass, copper, silver, and gold melt ? 



Brass at 1869 ; copper, 1996 ; silver, 1873 ; gold, 

 2016. 



860 At what temperature does cast-iron melt ? 



At 2786. 



861 What is the greatest degree of artificial heat which we have been 

 enabled to measure f 



A furnace heat of 3280 : at this heat wrought iron 

 and platinum did not melt. 



