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Description of a Method of Reducing Observations of Tem- 
perature, with a view to the Comparison of Climates. By 
Professor J. D. EVERETT, King’s College, Windsor, Nova 
Seotia, late Secretary to the Scottish Meteorological 
Society. 
The climate of a place, as regards temperature, involves 
three elements—mean temperature, range, and date of phase.* 
The first of these is subjected to measurement wherever 
meteorological observations are taken; the other two, and 
especially the third, have not received equal attention. These 
three elements appertain alike to daily and to annual varia- 
tions, but we shall confine our remarks to the latter. 
Annual range (¢. e., the range that occurs within the year) 
has been measured in various ways. Sometimes it is assumed 
as the difference between the two extreme readings which 
occur within the year; sometimes as the difference between 
the two extremes of daily mean temperature; sometimes as 
the difference between the mean temperatures of the warmest 
and the coldest calendar month ; sometimes as the difference 
between the mean temperature of a certain number of the 
warmest calendar months, and that of an equal number of the 
coldest. 
The two latter assumptions are defective in point of acct- 
racy, because the times of maximum and minimum are not the 
same for all places. It is obvious that the range, if estimated as 
the difference between the mean temperatures of two calendar 
months, will (ceteris paribus) appear greatest when the maxi- 
mum and minimum fall precisely in the centres of the two 
months ; and if this condition is more nearly fulfilled at one 
of two places compared than at the other, the comparison will 
be unequal. ‘The same remark applies when the mean of 
three (or any other number of) warm months is compared 
with that of the same number of cold ones, and the ratio of 
* Phases are the successive states of an element which undergoes continual 
change. By “date of phase,” I mean the earliness or lateness uf the phases 
generally ; in other words, the earliness or lateness of the seasons, upon the 
whole, as regards temperature. 
