[ 6 3 r 1 
From the former of which equations, by taking the 
fluxions on both fides, will be had pbx?~ l yix q- 
qbxPyi—'y (=ti) = mx n y w ~ l x qbxtyi—'y. Whence* 
pbx? *y? = m x”y m ~ 1 j and therefore pby q ~ m+1 = 
mx n ~i > + 1 . And in the fame manner proper equa- 
tions, to exprefs the relation of x and y 3 may be de- 
rived, in any other cafe, and under any number of 
limitations. 
LXXXVI. Obfervations on the Alga Marina 
latifolia ; The Sea Alga with broad Leaves* 
By John Andrew Peyffonel, M.D. F.R.S, 
Tranfated from the French. 
Read April 13T TA.VING calf anchor at Verdun, the 
! 75*- XJL road at the entrance of the river of 
Bourdeaux, I was fiflhing with a kind of drag-net 
upon a bank of land, which was very fine and 
muddy. We collected a number of fea-plants, and 
among them the great broad-leaved Alga, which I 
did not know : and as the root or pedicle of this 
plant appeared to be very particular, I obferved it 
with attention. The following is its defcription, 
and the detail of my obfervations. 
From a pedicle, which is fometimes flat, and 
fometimes round (for they vary in thefe plants, and 
might be about three lines in diameter, and an inch 
high, of a blackifh colour, and coriaceous fubflance, 
approaching to the nature of the bodies of lithophyta), 
a Angle 
