76 Canadian Record of Science. 



the solution of the problem of the secular variation of 

 climate. 



In order to deal mathematically with phenological 

 dates, averages or means, it is necessary to indicate dates 

 and average or mean dates in terms of the day of the year 

 instead of the days of the month. For the conversion and 

 reconversion of such dates, all that is necessary to make it 

 convenient, is to have before the eye a list of the months 

 of the year with the number of the day of the year cor- 

 responding to the last day of each month, thus : 



DAY OF THE YEA.R CORRESPONDING TO THE LAST DAY OF EACH MONTH. 



January 31 July 212 



February .• .59 August 243 



March 90 September 273 



April 120 October 304 



May 1.51 November 334 



.June 181 December 356 



For leap years each number except that for January 

 would be simply increased by a unit. The 24th of May 

 would be simply converted to the annual date by adding 

 24 to the last day of April, thus: 120 + 24 = 144. The 

 165th day of the year would be found by subtracting the 

 next smallest number in the table from the date, thus : 

 165-151 (May) = 14 (June). 



Now, we may consider a phenological date to be a sort 

 of mathematical function of variables, several of which are 

 already being very systematically and accurately observed 

 and recorded by the meteorological departments of most 

 countries, such as the variations of temperature, of atmos- 

 pheric pressure, sunshine, precipitation. Then there are 

 local constants, such as latitude, elevation, slope, proximity 

 of bodies of water, and character of the soil. All of these 

 influences affect' the phenological date, and conversely the 

 date may be considered as a summation or integration of 

 all these and other more or less unknown elements. We 

 find that in the month of April the season is advancing 



