at Leith Fort every Hour of the Day in 1824 and 1825. 387 



BH : Bm = HA* : win* ; and 

 BH x mn? 



Bm = 



HA* 



But since AE is the line of mean temperature, pn the depres- 

 sion of the temperature below the mean at the point of time p, 

 and pn = Hm = HB Bm, then, calling p the mean tempe- 

 rature, and y the ordinate mw, we have the required tempera- 

 ture T at the time p, thus : 



T HB j. HBx .V*- 



= '" l+ HA 



or if m is the minimum temperature of the daily curve, then, at 

 the point of time p, we have 



For the semi-parabola BC, the formulae are as follows : 



T HBx 



I = m H pr 



CH* 



For the semi-parabola CD, in which the required tempera- 

 tures exceed the mean, we have at any point of time p, 



or calling M the maximum temperature of the daily curve, 



For the semi-parabola DE, we have the following formulae : 



T L rr 



1 = (it + UD -- EG* ' 



EG* 



Upon comparing the parabolic abscissae in column 3. with the 

 observed results in col. 2., it appears, that the greatest difference 



