Popular Science Monthly 



909 



Skating on Salt 



The idea of using crystalline 

 salts, such as the carbonates 

 and sulphates of sodium, potas- 

 sium and other substances 

 having like properties, has also 

 been suggested. The salts are 

 boiled and then poured direct- 

 ly on a water-tight floor, hav- 

 ing raised edges. The floor 

 should be laid in sections, by 

 means of a frame for holding 

 the melted salts. After they 

 solidify, the frame can be used 

 for an adjacent section. 



This same method has been 

 improved so that a good per- 

 manent sliding-surface is ob- 

 tained. When the rink be- 

 comes badly scratched, due to 

 excessive use, heat is applied 

 by means of a. rectangular 

 frame supporting a wire lattice- 

 work. The frame is placed on 

 the floor and a rubber bag, filled with 

 steam, is laid on the lattice- work. The 

 action of the heat melts the salts, so that 

 a flat, smooth surface is formed. 



Another device for heating resembles 

 an ordinary garden rake. Steam is 

 blown on the floor through a longitudinal 

 slit in a tube. The tube has a handle 

 and two runners for guiding it across 

 the floor. The pipe for supplying the 

 steam passes down the handle and 



Intersecting channels underneath the salts are filled 

 with water to be taken up by the porous layer 



POROUS SUBSTANCE 

 MAGNESIUM CHLORIP. 



CRYSTALLINE SALTS^ 



The porous substance permits the surplus moisture to 

 pass from the magnesium chlorid to the crystalline top 

 layer or vice versa 



connects with the lower horizontal tube. 

 This smoothing process is too frequent- 

 ly necessary, owing to the varying 

 degrees of humidity in the atmosphere. 

 To do away with this difficulty, at least 

 partially, one inventor places a thick 

 sheet of sodium carbonate upon a layer 

 of porous material, which, in turn, 

 rests upon a floor having many inter- 

 secting channels. Water, circulated 

 through these channels, is absorbed by 

 the porous material and thus 

 comes into contact with the 

 top layer. This tends to pre- 

 vent the air from affecting 

 the sodium carbonate, but 

 does not completely overcome 

 the difficulty. 



The nearest approach to 

 perfection is a combination of 

 substances now l^eing used in 

 Germany with success. Be- 

 low the porous layer is a sheet 

 of some hygroscopic (water- 

 attracting) substance such as 

 magnesium chlorid. When 

 the air is humid, the excessive 

 moisture from the crystalline 

 top layer passes into the mid- 

 dle porous layer, and then 

 into the bottom layer; when 

 the air is dry, moisture reaches 



