I SO ON SURFACE WAVES PRODUCED BY SLEDGES. 



A long series of cahots was very quickly produced upon the 

 frozen St. Lawrence in snow about 10 inches deep; indeed, it 

 was surprising to see how soon the flat snow surface was thrown 

 into waves by the sledge traffic. In one of the streets of 

 Montreal I saw the old cahots being hacked up and the snow 

 road re-laid ; the material having consolidated to the consis- 

 tency of ice. In January and February, during the greater cold 

 at Winnipeg, Manitoba, the snow did not form cahots. When a 

 snow drift had consolidated across a road there would be seen 

 one or two slight undulations, obviously made by the bumping of 

 the sledge in passing over the obstruction, but they were not 

 remarkable. Cahots are known in other countries besides 

 Canada. Dr. Markoff informs me that they are familiar to him 

 in Russia, and the late Mr. E. A. Floyer drew my attention to 

 the following description in Wallace's " Russia." Apropos of 

 sledge travelling the author says : 



"The road soon gets cut up, and transverse furrows are 

 formed. How these furrows come into existence I have never 

 been able clearly to comprehend, though I have often heard the 

 phenomenon explained by men who imagined they understood 

 it. Whatever the cause and mode of formation may be, certain it 

 is that little hills and valleys do get formed, and the sledge as it 

 crosses them bobs up and down like a boat in a chopping 

 sea." 



The present writer also has often listened to the explanation 

 of the formation of cahots by those who are familiar with the 

 phenomenon, and who do not usually consider it to be remark- 

 able. The usual explanation is as follows : The transverse 

 furrows are caused by the bumping of the sledge. They are only 

 produced, therefore, when something makes the sledge bump. 

 This is usually hardened snow, e.g., a " drift" blown across a 

 road in the lee of some obstruction. Sometimes, however, the 

 sledge starts bumping on account of a hole in the roadway 

 beneath the snow. 



This explanation is, as we shall see, only partial, but it is 

 correct as far as it goes. Given a considerable initial inequality, 



