EEPOET OF THE SECRETARY. 39 



pletetl, and will be seut to press during tlie coming year. This section 

 consists of tables and discussions necessary to reduce observations 

 taken at different times of the day to the true mean of the day, and 

 other general corrections of irregular observations, and hence it was 

 necessary that this should be prepared first. It includes — 



1. General remarlcs on the explanation and extreme cases of the daily 

 fluctuations of the temperature; investigation of the corrections to 

 the mean temperature from certain hours of the day to refer it to the 

 true mean of the day. 



2. Tables of times of sunrise and sunset for every tenth day of the 

 year, and between latitudes 23° and 00°. 



3. Applications of Bessel's circular function to represent the daily 

 fluctuation, (yearly average;) the results for twenty stations are given. 



4. CUissification of the daily flu(;tuation into six typical forms; epochs 

 of maxiauim and miuiuuim, and of mean values and daily range, (with 

 two diagrams.) 



5. Annual variation in the range of the daily fluctuation, (witli two 

 diagrams;) and extremes of daily fluctuation in December and June, 

 (with three diagrams;) also table of recorded daily range of tempera- 

 ture for every month and for certain stations. 



C. Variability of the temperature at any hour from the normal value 

 of that hour, specially investigated for Toronto, Mohawk, Philadel- 

 phia, and Sitka. 



7. Table of the mean values of the hourly, bi-hourly, or semi-hourly 

 observations of teniperature, for every month, at nineteen stations. 



8. Table of the daily fluctuations of tem})erature derived from the 

 preceding table, and showing, for every hour and for each month and 

 the year, the difference from the respective daily mean temperature. 



Self registering instruments are absolutely necessary for this kind of 

 investigation, and when their readings are applied will place the results 

 on a niore satisfactory footing, and one commensurate with the bnport- 

 ance of the subject. 



The following is the condition of the work, which has been continued 

 during the past year with the labor of two computers : 



1. Consolidated tables, giving the mean temperature for each month, 

 season, and the year, have been prepared for the following States, &c.: 

 Alabama, Alaska, Arizona, Colorado, Dakota, Idaho, Nebraska, West 

 Virginia, Greenland, Iceland, British North America, and part of New 

 York. 



2. A large number of observations made at Havana, Cuba, have been 

 computed and added to the general tables. Various other additions 

 have been made and many deficiencies supplied. 



3. About three-fourths of the annual means at the different stations 

 have been calculated, embracing about 7,000. 



4. The maxima and minima tables have been nearly completed. 



