Sir D. Brewster on the Law of Daily Temperature. 347 



corresponding to two or three ordinates, with opposite signs 

 whose sums shall be nothing; thus, 6 h. a.m. and 5 p.m. give 

 — 2-545 and + 2*576, whose sum is only 0°'031. 



In like manner we may choose, in reference to our conve- 

 nience, to select two times of observation, one of these being at 

 a given hour, and the other between two hours ; or it may be 

 more convenient to take two times of the day, both of which 

 are between regular hours. The following table shows these 

 hours, and the intervals between the times of observation, as 

 deduced from the Leith observations. 



If it is more suitable to have none of the hours an even 

 number, we may combine the equal ordinates opposite 1 h. a.m. 

 and 1 h. a.m. in the preceding tables, thus — 



11 h. 34 m. a.m. and 5 h. 45 m. p.m. 

 11 49i 5 18 



and so on with the other numbers. 



The difference between the Leith and Inverness ordinates, as 

 shown in the table, page 346, exhibits the effect of an increase 



