124 Construction of Galvanic Magnets. 



Dutrochet's views with regard to absorption, &c., and make the 

 appUcation of them to account for phenomena of this nature, 

 such a state would be, if not necessary, at least most favorable 

 to such processes. 



I have given this long description of a formation which ap- 

 pears to me somewhat curious, in hopes that you may find some- 

 thing in it to interest you. I will not apologize to you for de- 

 scribing a kind, of formation which is so far from being rare ; for 

 I am well aware that in addressing you upon this subject, my 

 motives will be a sufficient apology. 



Remark. — We should like to compare this bituminized wood 

 with well characterized lignite. — Eds. 



Art. XVI. — The Constructio7i of Galvanic Magnets ; by John 

 B. Zabkiskie, M. D., of Flatbush, N. Y. 



Many experiments are still wanting to establish the best pro- 

 portions of galvanic magnets, and the most advantageous mode 

 of using them; such as the best shape of the iron, the maximum 

 size of the bar, the relative weight and best form of the winding, 

 the most advantageous mode of communicating the galvanic cur- 

 rent to rotating magnets, &c. 



That the shape of the iron used in constructing galvanic mag- 

 nets will tend to vary the result of their action, must be evident 

 upon reflection. If we take as an example a common horseshoe 

 galvanic magnet, the most active parts are the two extremities; 

 and although every portion of the iron contributes its effect from 

 induction, still this effect is continually decreased until it reaches 

 the center, when it is reduced to nothing. If then we divide the 

 iron in a magnet of this description (Fig. 1,) into five equal parts, 

 the iron in A may be considered as nearly 

 inert, and that in B and C as more powerful, 

 but still far inferior in power to D and E. 

 The part A, may then be considered as near- 

 ly useless as far as its own original effect is 

 concerned, and useful only by acting as a 

 bond of union between the two extremities 

 of the magnet by conduction. Any form of 



