DECOMPOSITION OF WATER. 355 



upon a sheet of india-rubber at the bottom of the vessel to keep the metal 

 in the tube, for when the necessary explosion takes place the mercury might 

 also be driven out. A spark from the electrophorus or from a Leyden jar 

 may now be passed through the gases in the tube. The explosion occurs, 

 and water is formed inside. If the mercury be again admitted it will rise 

 nearly to the very top of the tube, driving the bubble up. Thus we find 

 we have formed water from the two gases. 



The decomposition of water is easily affected by electricity, and if a 

 little sulphuric acid be added to the water, the experiment will be thereby 

 facilitated. Two wires from a battery should be inserted through a glass filled 

 with the water, and into two test tubes also filled. The wires terminate in 

 platinum strips, and are fastened at the other end to the positive and 

 negative poles of the galvanic battery. The gases will collect in the test 

 tubes, and will be found in proper proportions when the current passes. 



Fig. 3*4- The Eudiometer. Fig. 345. Decomposition of water. 



So much for water in its liquid state. The solid condition of water 

 (ice) is equally interesting. When we apply heat to water, we get a vapour 

 called "steam"; when we cool water to 32 Fahr., we get a solid mass which 

 weighs just the same as the liquid we have congealed, or the steam we 

 have raised from an equal amount of water. But water expands while in 

 the process of solidification, just as it does when it becomes gaseous, and as 

 we have remarked before, our water-pipes bear full testimony to this scientific 

 fact. When ice forms it has a tendency to crystallize, and some of these 

 ice crystals are, as we see, very beautiful. Snow is only water in a nearly 

 solid form, and the crystals are extremely elegant, appearing more like 

 flowers than congealed water, in tiny six-pointed ice crystals. Many 

 philosophers of late years have written concerning these tiny crystals, which, 

 in common with all crystals, have their own certain form, from which they 



