158 On the Measure of 
immersed three inches under the surface, and 
found that it supported a weight of 19.45 liv, 
which, by the theory, should have been 
only 8.75 liv.* | M. de Prony attempts to ac- 
count for the results obtained by Don Juan, 
by the additional pressure occasioned by the 
surface of the water over the plane being raised 
higher than the general level of the current. 
That circumstance, however, can account for 
a small part only of the difference. -M. du 
Buat explains his experiments by his theory 
of non-pressures, which I have already shown 
to be fallacious. 
M. du Buat has diowmriberd other experiments 
which are considered by some to accord better 
with the theory.t ‘They were made upon insu- 
lated veins of water, spouting from the per- 
pendicular side of a vessel against a surface 
not greater than the section of the vein; and 
from their results he draws the following 
conclusions: “ Il résulte des expériences qui 
précédent, que le choc d’une colonne ou d’une 
veine fluide contre une surface de méme 
étendue & directe, est sensiblement égal au 
produit de cette surface, par la hauteur die 4 
la vitesse. L/intensité du choe dépend néan- 
moins en partie de la liberté plus au moins 
* Priucipes d’hydraul. yol. 2. p, 218. et Ibid, p. 142, &e, 
