32 



THE POPULAR SCIENCE MONTHLY. 



of particles liave the same general configuration as the finished 

 ornaments hundreds of times as large six to eight inches wide 

 at the base and projecting twelve to sixteen inches. A slight 

 variation in the direction or velocity of the wind makes them 

 more complex and adds greatly to their beauty ; but a change of 

 as much as sixty degrees in the direction wrenches them from 

 their supports. They come away entire, and lie in heaps under 

 the trees like autumn leaves, and may be collected and preserved 

 in a cold, sheltered place until they gradually evaporate. 



The process of formation is an interesting study. It is impos- 

 sible to follow the course of the fine particles of snow dust which 

 make up the most beautiful forms ; but at a temperature of 

 twenty-five to thirty degrees above zero the frozen moisture 



Fig. 4. 



comes in minute pellets of ice which may be watched with a good 

 microscope as they strike a chosen spot. The development of the 

 ice-forms is much more rapid than that of the snow- forms ; other- 

 wise the processes seem to be identical. 



On the edges of fiat surfaces, and along the diameters of round 

 bodies, lines of particles are deposited as the wind rushes past the 

 obstruction. Then begins a twofold growth, caused by the direct 



