780 Transactions of the American Institute. 



When we heat water up to the boiling point, the rotation of the 

 atoms around each other becomes more rapid until at last they fly 

 apart, and then they move in straight lines. That is a point that is 

 not new. Prof. Barker, in his new chemistry, states that the atoms 

 in gases move in straight lines. That motion becomes more rapid as 

 the temperature rises ; and as the force of impact increases with the 

 .square of the velocity, that explains why the pressure of steam 

 increases so much when we raise the temperature. It has been shown, 

 also, by the diffusion of gases, that the particles must move either in 

 continuous rectilinear motion or in very much elongated ellipses. 

 Hydrogen gas moves with greater velocity than other gases. Gases 

 diffuse differently according to the square root of their density, 

 The density of hydrogen gas is l-16ththat of oxygen gas; and there- 

 fore four times as much hydrogen will pass through a given space as 

 of oxygen, in the same time. All these facts tend to show that the 

 particles of gases move in straight lines. 



Let us go a step further, and apply that to the heat of disassocia- 

 tion. It has been suggested that the spaces between the atoms, com. 

 pared with the sizes of the atoms, are as large as the planetary spaces 

 compared with the sizes of the planets. In steam, the particles move 

 in straight lines, but they move jn triplets, two atoms of hydrogen 

 and one of oxygen all sticking together and forming an atom of steam ; 

 but when we reach the heat of disassociation, the atoms of hydrogen and 

 oxygen move independent of each other. On the other hand, if the 

 disassociated gases, above 5,000° Fahrenheit, are cooled to that point, 

 they will unite, or combustion will take place. That is continually 

 taking place in the sun, as shown by the spectroscopic observations 

 upon the corona ; and it takes place in the stars. But a few years ago 

 you will recollect that a star in the northern crown suddenly shone out 

 with great brilliancy, and it was ascertained that the light was from 

 flaming hydrogen. They cool down until they reach the point where 

 association can take place, and then they burst into flame. The heat 

 developed by the combustion may raise the temperature to the point 

 of disassociation again ; and then it may require a long period before it 

 will cool down so that combustion can again take place. 



"We may consider the formation of hydrogen and oxygen first into 

 steam, then into water, and then into ice, as a descending temperature 

 along inclined planes and precipices. The elementary gases descend 

 an inclined plane until they reach the point of association. They then 

 fall down a precipice, and 8,000 units of heat are set free. Then they 

 come down another incline for 5,000° until the steam reaches 212°, 



