Notice of a Galvanometer. 103 
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leaves may assist in the elevation of the sap. After their expansion, 
not a particle of sap will flow from the wounded vegetable. They 
assist in this process by the rapid evaporation from their surface. 
That they may accomplish the functions assigned them, they seem to 
be fitted to the various situations in which they grow. In tropical 
climates they are largely expanded, in cold regions they are narrow, 
contracted and rigid. ‘The circulation of vegetables is not entirely 
suspended during the winter. As we may still see the buds gradu- 
ally enlarging, especially in sheltered places. As the vegetable 
draws its nutriment from the bosom of the earth, beneath its ice- 
bound surface, we find it preserving an elevation of temperature 
above the circumambient air. I wish to present the above remarks 
rather as hints, than established conclusions; they are offered for the 
purpose of calling the attention of philosophers anew to the subject, 
that something more satisfactory may be taught than we find in the 
existing systems of vegetable Physiology. 
Williams College, Dec. 12, 1833. 
Art. XIV.—Votice of a Galvanometer; by Dr. Joun Locke. 
TO THE EDITOR. 
Dear Sir.—The galvanometer concerning which, I wrote to you 
last spring has been changed, again and again, until I have finally con- 
structed an instrument with which I am satisfied. ‘The essential part 
of it is a wire wound around a flat ring of boxwood. The outside 
diameter of this ring is 3.75 inches, and the inside diameter three 
inches. Its thickness is one fourth of an inch. The outside edges 
of it are cut or notched like the teeth of a clock wheel, in order to 
cause it to hold the spiral wire which is coiled around it in a sin- 
gle layer, the several parallel turns as close as possible without be- 
ing in contact; except at the diameter of the ring, where an open- 
‘ing of the tenth of an inch is left for the introduction of a mag- 
netized needle within the coil. ‘This flat coil is put into the bot- 
tom of a cylindrical mahogany box turned in the shape of a snuff 
box, four and a half inches in diameter and one and a half deep, 
outside dimensions; the projecting ends of the wire being passed 
through, near the bottom of it. Immediately above this coil is the 
card or divided circle, which is attached to a thin wooden ring. 
The needle is suspended by asilk filament. It is made of a simple 
