52 
Description of the Animal of Ampullar i a. 
the two expressions are equivalent, and by transformation will become 
h s e ( F' — f) 30 . „ Lae (¥' — f) 30 
i = w~B or substituting for i, c f r = mTB ’ 
Let r — S' i •) n' n' being a co-efficient determined from experiments with a ther- 
mometer. the surface of which = s' and mass (expressed in grains of water)=M>', and 
(f ’) representing the part^olar function which r is of nJ Then /or any other 
s tn' 
thermometer with surface s and mass ?^,the value of r will be /') n ' — ; 
J ' s' tv 
In like manner, let c = (f) n for surface s' and mass tv'. For s and «?, it will be 
s w' 
(f) 71 fff 
Now substituting these values of c and r we have 
■ . .V w' j . .. 9 v' h s e (¥' — ' ) 30 
(f)ri — +(/'; n = 
J ' s' m ' * tv w B 
^ , w' w' Ij e fY' 
Dividing by — f/J L r/'>'— = — J ■ 
From this change of the equation, we see the reason why, whatever the size and 
shape ol the thermometer, the depression is still the same, no function of the 
size or shape being found in the equation, n — is a constant quantity from what- 
ever thermometer it be determined, because it is certain that n varies inverse- 
i w ' 
v as -pr tae product must therefore continue the same. 
With regard to the nature of the functions (f) (f,) MM- Dulong and Petit hare 
determined them apparently with every accuracy, n ~ must be found from ob- 
servation. A table of the values of L may be found in a late No. of the Quarterly 
Oriental Magazine, a id of F and/ in the article Hvgrometrv before referred to": 
oth^lS dte-.Sio y T Dalt0n ! but f “S triaL Ude ^ m^^ 
subject in ; b d,,eS " ot a PP ear satisfactory- I shall resume the 
bv Spmi,^ thT resnlT; 'rlTr'" d “ *" d th <** several particulars, and 
IT. Description of the Animal of Ampullaria, a Genus of frech- 
mg observations on the animal inhabiting the shell olFerin K the foUow : 
j r,;s,s c "™'' - - »»'■* »» u» 
i&!3& IS &!»„ >;,» Wi tally -r 
is stated in Dubois’ Epitome to I... ,i, 1 <*ludina and Valvata. The animal 
=p;in,^ 
at the e«S‘ bte'of ~ of pedicles situated 
^es are placed on the t^taculm at ^enta ; while in Paludina the 
thickness of the tentacuST^ ® 2" a th } rd of th cm length. The great 
mentioned genus the pedicle, which “JPIwWonftbM in tie W- 
“ *• “““>■• * 
