Diurnal Variation of Temperature. 213 
tems congruous. And it will be seen that in determining the 
diurnal variation of the temperature (pp. 412-414) and its ex- 
pression by the goniometric formula, five daily observations 
D 
Mid really employed instead of three only as stated by Dr. 
i 
It is, however, not this circumstance which leads me to make 
a public rejoinder; but the general principle involved. For as 
regards the diurnal barometric variation, the constants of the 
sine-formula have in truth been deduced from the results of 
as 
— which serve the purpose of additional equations. 
hot very long before sunrise, furnish the requisites for deducing 
four constants from observations made at proper intervals three 
appears to me that any just criticism of the investigation must 
rather be directed against the propriety of these hypotheses, 
than against the legitimateness of the method. 
There is yet another consideration which, although not fully 
set forth in the printed volume, has guided me in the course 
which [ have pursued, and in which I purpose to continue, in 
the Investigation of the climatic constants for other points in 
South Ameri 
and not very remote places accord in confirming the general 
resented by the sine-formula with only three variable terms. 
The object of the investigations is to attain a knowledge of the 
true laws. If there really are laws, they must be capable of 
xpression by some algebraic formula; and numerous tests 
