OF TEMPERATURE AT TORONTO IN CANADA. 
The temperatures at the several hours of the day and on the several days of 
the year, computed in the manner which has been described, furnish data for 
the delineation of the Chrono-Isothermal Lines in Plate X. figs. 1 and 2. The 
representation in this Plate of the phenomena of the temperature at Toronto is on 
the same principle which has long been used in maps of the magnetic isogonic, 
isoclinal, and isodynamic lines, in which three variables are comprehended, of which 
one, the magnetical element, is dependent upon the other two, viz. the geographical 
latitude and longitude. The principle is also the same as that adopted in ordinary 
isothermal maps ; but, whereas in those maps the two variables upon which the 
meteorological variation 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 the temperature is here referred to time and not to space. This 
difference is intended to be conveyed by the term Chrono-Isothermals as applicable 
to lines of the present description, whilst those of the more customary form might 
not inappropriately be termed, for contradistinction, as suggested to me by Mr. 
Wheatstone, Topo-Isothermals. Representations of the Chrono-Isothermals in 
different localities might materially facilitate the comparison of the phenomena of 
the temperature in different parts of the globe ; and if similar plates were constructed 
for each of the meteorological elements at the same locality, they might be useful 
for intercomparison, and for illustrating the mutual dependence of the elements on 
each other, to those who prefer a representation to the eye to the instruction con- 
veyed by tabular abstracts. In fig. 1 the isothermals are represented which are 
comprised between the mean temperature of the year and the highest isothermal ; in 
fig. 2 between the mean temperature and the lowest isothermal. In fig. 1, conse- 
quently, the isothermals increase in value from the circumference to the centre ; 
whilst in fig. 2 they decrease from the circumference to the centre. To avoid too 
great a multiplicity of lines only every alternate degree (the even degrees of Fahren- 
heit’s scale) are drawn. Figs. 1 and 2 are so arranged on the Plate that the summer 
and winter solstices (marked by a dotted line) are in the same vertical. I'he ab- 
normal character of the winter temperature of the North American Continent is 
strikingly manifested in this Plate. 
From the temperatures computed from the six years of observation and represented 
in the plate, we learn many facts regarding the temperature at Toronto, which are 
interesting in themselves, and may become particularly so in their comparison with 
the phenomena in other parts of the globe. Amongst these may be noticed the 
following : — The mean annual range, or the difference between the mean temperatures 
of the coldest and hottest months (February and July), is 42°'7. The warmest day of 
the year is July 28, being thirty-seven days after the summer solstice. The coldest 
day is February 14, being fifty-five days after the winter solstice. The mean 
temperature of the year is passed through on April 19 and October 15. The warmest 
and coldest days, and the days on which the mean temperature is passed through, 
