30 THE ROYAL SOCIETY OF CANADA 



to form during the Winter season. He describes his observations as 

 follows: — 



"Early in the Winter of 1910 the Superintendent in charge of 

 one of the Rangeley Dams was instructed to be on the watch for the 

 formation of reefs, and about the first of January, 1911, information 

 was received of the formation of reefs on Lake Mooselucmeguntic, 

 and a party was immediately sent to study the formation and to gather 

 information from residents in that section. 



"Following are the conclusions reached after investigation, making 

 observations, and sifting the evidence. 



"The ice first cracked at the site of the reef during a cold period 

 about December 22nd, 1910. 



"On January 2nd there was a rise in temperature from 3° below 

 zero to 41° above. 



"A large reef was formed about 10.00 a.m. on January 2nd, 

 1911. 



"When reefs form they do so near the same location each year. 



"Reefs form in a warm period preceded by a very cold one, and 

 may form at night if the temperature is rising. 



"Reefs generally form when the ice is free from snow, or at least 

 with very little upon it. 



"Reefs do not always occur where there is a crack in the ice 

 neither do they always rise, as occasionally one sheet may slide under 

 another. 



"Reefs act for a time as expansion joints, — that is the peak of 

 the reef may rise and fall with expansion and contraction of the ice 

 sheet. 



"They seldom occur when the ice is over a foot thick, but in- 

 stances are known where they have been formed with ice twenty 

 inches thick. 



"They are generally higher at the middle of the lake than at the 

 shores. 



"No pushing up of rocks or soil is noticed in bays or inlets." 



