285 



for the hour in the manner described, — the non- periodic variations 

 for every day in the year are obtained and are given in a table. 



From the approximate normal temperatures the author has repre- 

 sented in a Plate the phenomena of the temperature at Toronto, ac- 

 cording to a method which, if applied to the different meteorological 

 elements and in different localities, might, he thinks, materially facili- 

 tate their intercomparison. This method, in which three variables are 

 represented, one being dependent on the other two, is essentially the 

 same that has been long used in magnetic maps, and in the ordinary 

 isothermal maps ; from which latter however it differs in this respect, 

 that, whereas in the ordinary isothermal maps the two variables on 

 which the variation of temperature is dependent are the geographical 

 latitude and longitude, in the present case the two variables are the 

 hour of the day and the day of the year. The variation of tempe- 

 rature is here referred therefore to time and not to space-, a distinc- 

 tion which the author proposes to convey by employing the term 

 Chrono-Isothermals, as applicable to lines of this description. From 

 the delineation in the Plate, and from the tables contained in the 

 paper, many characteristic and some peculiar features of the climate 

 and meteorology of the part of the North American Continent in 

 which Toronto is situated, are readily perceivable. Several instances 

 are pointed out; amongst these may be noticed the peculiar ano- 

 maly of the r^orth American winter, which is very conspicuous in 

 the Plate ; and the absolute as well as relative variahility of the tem- 

 perature at different seasons of the year, exhibited by means of a 

 numerical index analogous to the probable error of the arithmetical 

 mean of a number of partial results, and deduced in a similar man- 

 ner from the differences of individual years, months, and days, from 

 their mean values : whence it appears, in respect to the annual 

 temperature, for example, that in any particular year there is an equal 

 probability that its mean temperature will fall within the limits of 

 43°' 6 and 44°* 9, as that it will exceed those limits on either side. 



Finally, the author has shown the " Thermic Anomaly" (as it has 

 been recently termed) of the monthly and annual temperatures at 

 Toronto by comparison with the normal temperatures computed by 

 Dove (Verbreitung der Warme, 1852), for the parallel of 43° 40' N. 

 from 36 equidistant points on the parallel; from which comparison 

 it appears that after allowance has been made for the elevation above 

 the sea (342 feet), every month of the year is colder than the normal 

 temperature of the same month in the same parallel ; that the thermic 

 anomaly reaches its extreme in February, when it exceeds 10° of 

 Fahrenheit ; and that on the average of the whole year it is little less 

 than 6°. 



Proceedings of the Royal Society. Vol. VI. No. 95. 20 



