428 Hail and Snow. 



of human skill and human knowledge, we shall observe the uti- 

 lization of scientific discoveries, and their applications to prac- 

 tical purposes. There is often a very wide space between the 

 discovery of a principle in the laboratory and its application in 

 the workshop or the factory ; but the mission of philosophy is 

 fulfilled only when the discoveries it has made have been turned 

 to the benefit of mankind. One of the greatest advantages of 

 such exhibitions as the present is, that all the marvels of art 

 and science, all the fruits of ingenuity and perseverance being 

 gathered together under one mighty roof, everyone may 

 learn what science has achieved, and what principles have been 

 applied to practical purposes. Of the millions who wander 

 through this maze of wonders, many, no doubt, are occupied in 

 considering what may be done in addition to what has been al- 

 ready done, what new material may be utilized, what old pro- 

 cess may be improved or what new one suggested, what novel 

 application may be made of the countless principles that are 

 suggested in this vast assemblage of all that man has discovered 

 and all that he has achieved. 



HAIL AND SNOW. 



BY ALEXANDER S. HEESCHEL, B.A. 



All who have examined attentively the feathery down that 

 forms the crystals of a snow-flake, and the compacter pellets of 

 ice that characterize a hail-storm, will have asked themselves 

 the question, What is the origin of so curious a difference in 

 their structure ? The answer is by no means long, and may 

 be considered at this time to be pretty firmly established. 



The most careful balloon ascents of the last and present 

 centuries have shown that for every mile that ascent is made 

 above the earth, the thermometer sinks 15 Fahrenheit degrees. 

 It is a practice pretty commonly known, to estimate roughly 

 by pulses of the wrist the distance of lightning flashes from the 

 spectator, six pulses being reckoned to the mile until the first 

 peal of the thunder is perceived ; and many persons will have 

 noticed as a fact that while near flashes of liohtning are followed 

 shortly by drenching rains, falls of hail are more commonly 

 ushered in by distant flashes, which they follow at greater in- 

 tervals of time. A flash of lightning is generally understood 

 to announce the formation of more or less large drops of rain. 

 The sudden refrigeration of a large highly aqueous tract of the 

 atmosphere, converts the vapour which it embodies to mist, the 

 small particles of which, descending and overtaking each other, 



