168 ROYAL SOCIETY OF CANADA 



to crystallize. Here is a cooling device — metal bars in the winter wind 

 — often 50° or 60° below the freezing point — with an unlimited amount 

 of nature's energy behind it, lowering the temperature of the iron rack 

 and, by conduction, of the water surrounding the rack. The design 

 of artificial ice-making plants is quite similar to this. 



The necessity for a blacksmith to use tongs for tlie protection of his 

 hands from the heat of the iron which he is fashioning is an old and 

 well-known illustration of the heat conducting property of iron. Un the 

 other hand wood is such a poor heat conductor that a wooden rack has 

 practically no cooling effect on the water and, consequently, frazil does 

 not crystallize upon a wooden rack as it does upon an iron one. 



The tail races of some power plants are also left exposed to the 

 action of cold air, as shown in Fig. 3, and the temperature of the heavy 

 metal draft tubes becomes lowered by the surrounding air. By con- 

 duction the water-wheel's whole case becomes chilled and its tem- 

 perature is probably several degrees below the freezing point. My ex- 

 perience has been that these exposed or neglected plants are more sus- 

 ceptible to frazil troubles than others which .are protected from the air, 

 and these points of explanation, as to the cause, are such very reasonable 

 ones that they are now agreed to by all who have given this subject 

 serious consideration. As the temperature of the water itself never falls 

 very low, it always stays vnthin a few thousandths of a degree of the freez- 

 ing point — and as water has such poor heat conducting qualities — about 

 120 times less than iron — it is most desirable, in my opinion, to keep the 

 metal completely covered by this warm (comparatively speaking) water 

 " blanket " rather than leave it exposed to the action of the cold air 

 which may be 70 degrees below the freezing point. 



The foregoing statements illustrate my mental attitude in relation 

 to the frazil question at the time when I was fortunate enough to pick 

 up a paper entitled : " Ice Formation and Precise Temperature ![lVIeasure- 

 ments," written by Dr. Barnes to whose work reference has already 

 been made. Tlie reading of Dr. Barnes' work filled me with a desire to 

 carry out some experiments, and, these experiment? — carried out in the 

 face of much adverse criticism, absolutely no encouragement, and, some 

 ridicule — were successful beyond the dreams of hope or imagination. 

 They may be summed up with the statement that a set of water wheels 

 overwhelmed by frazil, in the condition of that illustrated in Fig. 8, can, 

 by the simple opening of a steam valve and the application of a little 

 heat, be cleared of frazil in a few minutes. (It formerly took a greater 

 number of hours, as pointed out above.) By the earlier application of 

 a little heat, frazil will not accumulate around them at all, and the plant 

 can be kept in continuous uninterrupted operation. 



