Notice of a Galvanometer. 1 03 



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. — Notice of a Galvanometer; by Dr. John 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, w r here 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 a silk filament. It is made of a simple 



