Diurnal Variation of Temperature. 121 
The data thus collected afford some opportunity for general- 
ization; but this we reserve for some future occasion ; sim ] 
the average epoch of maximum from 2 P. -M., and to the large 
those deduced for th several months. The ee tendency of 
the interval, between the minima and true sunrise, to increase 
with the latitude i is mts readily sarge This is of course 
due to the sun’s near approach to the horizon long before its 
actual arrival there. 
esiring a rough test both of the average epoch of max- 
imum, as deduc ed from a short aes od of obs ervation, and of 
, t 
indebted for our meteorol soa observations, asking them to 
note the temperature half-hourly for a pe eriod of some hours 
which should include the epochs of maximum during ten or 
twelve successive days. 
These pPrereasione referred to apparent time give the fol- 
lowing results: 
ee ee 
Place. Approx.Lat.| Period. | Mean Epoch |Uncertaintyof) Variation. 
| 
Bahia Blanca _____ 38° 45’ May gens 2h 13™ p, mM. 547 jh27m~_2h4gm 
Buenos‘ Aires_____ 34 16 |Apr.21-30] 2 22 4 1 2 -2 56 
8. Antonio de Areco| 34 13 | Apr. 21-30 2 194 1 38 -2 44 
Cc 2 14 34 127 -361 
ordoba ee 31 25 |May j)-90/ 2 11 6 11 28 -3 40 
Villa Hernandarias 31 15 |May I-14) 2 453 3 1 40 -3 28 
le. dod CO 9 |\May 1-10] 1 554 5 12 48 -2 48 
sem, nds 24 50 |Apr. 23-30] 2 38 4 1 14 -2 57 
The column entitled “ Uncertainty of ah epguenea con- 
tains the sum of the various estimated possible errors in plot- 
ting the observations, drawing the curves, and sending of the 
results. The limits of probable, or posible errors of the last 
two classes depend of course, princip ally, upon the form of the 
curve itself. The column entitled “ Variation,” contains the 
ifference between the — values on different days during 
the continuance of the 
it will be seen that pri ‘results confirm our previous infer- 
That the later terms of the formula should become more im- 
portant in high latitudes during the winter season is a manifest 
snp ba of the inequality of the two portions into which 
the minimum divides the interval between the normal epochs 
of maxi imum. When sunrise occurs so early as to render this 
