44 



REPORT — 1844. 



of the earth's rotation on its axis. It is a single progression ; having but one 

 ascending and one descending branch, the turning points being a maximum 

 early in the afternoon, and a minimum about sunrise. Each hourly mean in 

 each year in the subjoined table is an average of about 311 observations, 

 being one on each day, except Sundays, Good Friday and Christmas day. 

 Each hourly mean of the two years is therefore an average of about 622 ob- 

 servations. The mean temperature of each year, or of all the hours on all 

 the days of the year, rests on about 3732 observations ; and the mean tem- 

 perature of the two years on about 7464 observations. The very small 

 amount of the differences which the table exhibits in the results at the seve- 

 ral hours in 1841 and 1842, shows a probability that we have already deter- 

 mined the diurnal march of the temperature, (as far as it can be obtained 

 by two-hourly observations,) with a very near approximation to the truth*. 



If we take the difference between the mean temperature at Toronto derived 

 from all the observations (44°'4), and the mean of all the temperatures ob- 

 served at each of the observation hours, we have the mean diurnal march of 

 the thermometer as shown in the table, or how much the temperature amount 

 is above or below its mean at each hour of observation. 



In the line immediately beneath the diurnal march of the temperature at 

 Toronto, is placed the diurnal march at Prague, by which means the general 

 resemblance and the minor differences can be at once perceived by the eye. 



These latter are further shown in the last line, which points out the 

 hours when the temperature is proportionally warmer at Toronto than at 

 Prague, which hours have a + sign before them, and those when it is pro- 

 portionally colder, which are characterized by the — sign. It will be at 

 once obvious that the climate at Toronto is proportionally warmer during 

 the hours of the day, and colder during those of the night, than at Prague. 

 Toronto being in a lower latitude and therefore nearer the sun, the sun's in- 

 fluence is proportionally greater during the hours of the day ; but in the 

 absence of the sun, the powerful causes which, in spite of the difference 

 of latitude, depress the isothermal lines, show their unchecked influence in 

 the proportionally lower temperature of the hours of the night. So strong 

 indeed are those causes, that at no one hour of the twenty-four does the 

 absolute temperature at Toronto rise to an equality with that of Prague. 



* The building of the observatoiy at Toronto having been completed in September 1840, 

 the observations now under notice commence with October 1840. The year 1841 in this 

 communication is therefore more strictly the year which commences October 1, 1840, and 

 ends September 30, 1841. In like manner 1812 commences with October 1, 1841, and ends 

 with September 30, 1842. 



