378 Improved modification of Dr. Locke’s Galvanometer. 
Culm 6—10 inches high, triquetrous, smooth, leafy towards the 
base; leaves flat, soft, sheathing, upper ones long as the culm; stig- 
mas three ; spikes three’or four, sub-umbelform, upper one oblong, 
staminate below; the others pistillate, ovate or oblong, subsessile, 
bracts longer than the culm; fruit oval, roundish, triquetrous, orifice 
entire, light green; scale ovate or oblong, acute or somewhat obtuse 
on the same spike, shorter than the fruit, and black. 
- Found in Alpine meadows of Lapland; and by Dr. Richardson, 
on the Rocky mountains, and also at the sea-coast of the Arctic re- 
gions of America, full in fruit June, 1826. 
Figures of two Carices are in this volume $ 
C. Baldwinia, D. Tab. T. fig. 61. 
C. venusta, do. 62. 
Art. XV.—Communications by Dr. Jonw Locke, of Cincinnati. 
I. Improved modification of Dr. Locke’s Galvanometer. 
Cincinnati Female Academy, Feb. 14, 1834. 
TO PROFESSOR SILLIMAN. 
‘Dear Sir—in my last, I sent you some account of my galyano- 
meter as finally made in the discoid form on a wooden ring. My 
communication was accompanied by a drawing of the instrument 
as enclosed in a cylindrical box. I now communicate to you an im- 
provement which I have since made by adding a stationary magnet 
to neutralize the effect of the earth’s magnetism on the needle. 
This magnet I have adapted to the brass tube which rises. from the 
center of the glass cover, and encloses the filament suspending the 
needle. It is two and a half inches long, Pp 
and one eighth of an inch in diameter, 
having a large perforation in the middle, 
in which is inserted a short piece of 
brass tube having an inside diameter 
adapted to the suspension tube of the in- 
strument. The tube and the magnet thus 
connected surmount the instrument with 
an ornamental cross. ‘T The suspension 
tube. P the ivory pin for winding the | For the drawing of the rest of 
: : this instrument, see p. 105 of this 
filament by which the needle is suspend- yolume. i 
