SCIENTIFIC NOTES. 



THE ACCIDENT OF TEMPERATURE. 



EVERY text-book on elementary science announces the fact that 

 there are three distinct states of aggregation of matter, spoken 

 of more simply as states of matter, flatter, they say, exists m three 

 distinct forms commonly called solid, liquid, and gas or vapor; and 

 on the molecular theory, these conditions are to be explainefl by dif- 

 ferent arrangement and speeds of the molecules which form them. 

 The points where the different states merge or change abruptly mto 

 one another are known as the freezing, or melting points, and the 

 boiling, evaporation or condensation points. The main factor m 

 determining the particular state in which a body shall occur is the 

 temperature and intimately related is the pressure which acts upon 

 the body. In fact the temperature and pressure are the great varia- 

 bles of the universe, determining as they do to large extent the 

 entire range of physical processes. In certain cases through limited 

 range of temperature and pressure the volume is the regulator of 

 the amount of each state in a mixture of two. The transition from 

 one state to another is always marked by many phenomena, e.g., 

 when ice freezes there is an abrupt change in volume, a remarkable 

 evolution of heat, a decided change in the value of the specific heat 

 (it being reduced to one-half its former value), and its other pro- 

 perties being changed in some degree. The change of water into 

 steam is accompanied by even greater changes in volume and specific 

 heat and a much greater absorption of heat. 



When we reflect that water boils normally at 100°C. and freezes 

 at 0° C, that the highest artificial temperature (the electric arc) is 

 4100°, while the lowest yet attained (liquid helium) is about — 268°, 

 we see that the region in which water exists in liquid form is rela- 

 tively small. At very high temperatures water undoubtedly ceases 

 to exist as water, becoming dissociated into its constituent elements. 

 What is true of water is true of other substances. They have their 

 boiling and freezing points, and their properties change with the 

 temperature. At low enough temperature-all would be solid and at 

 high enough all would be gaseous ; and somewhere between these 

 extremes most would be liquid, so that the universe as we know it is 

 an accident of temperature. Next to air, water is the most important 

 factor in the support of life, and while life is almost universally de- 

 stroyed at boiling temperature, it is possible many degrees below 



