426 CONTENTS. 



COREESPONDENCE. 



Page. 



Sketch of the Navajo Indians. By J. Letheeman, M. D - 283 



Topography of Black Mountain. By Hon. T. L. Cling man 299 



Relative to the publication of Spanish works on New Mexico 307 



REPORTS. 



On Galvanism ._ 311 



Introduction. 311 



Section First. The Cheihcal and Contact Theories 311 



§ 1. Brief sketch of the Theories.. 312 



§2. Schonbein's Chemical Theory. _. 314 



§ 3. Comparison of the Contact Theory with Schonbein's 319 



Section Second. Determination of the Constant "Voltaic Battery. 320 



§ 4. Unit of force of current 320 



§ 5. Comparison of the different current units 323 



§ C. Reduction of Pouillet's imit to chemical measure. 324 



§ 7. Reduction of Weber's unit to the chemical measure .- _ 326 



§ 8. Determination of the force of a current by its chemical effects 327 



§ 9. Resistance of the element 330 



§ 10. Electro-motive force 337 



§ 11. Electro-motive force is proportional to the tension of the open 



battery. 338 



§ 12. Indirect methods for determining the Constants of the Battery.. 341 

 § 13. Poggendorff 's method for determining the Electro-motive force of 



inconstant batteries 346 



§ 14. Comparison of different Voltaic Combinations .- 349 



§ 15. The simple zinc and copper battery 350 



§ IG. Smee's battery 353 



§ 17. The zinc and copper battery, with two liquids 354 



§ 18. Grove's Battery. 355 



§ 19. Bunsen's Battery. 356 



§ 20. Zinc and iron Battery. 357 



§ 21. Iron and iron Battery _ 358 



§22. Callan's zinc and lead Battery 359 



§ 23. The most convenient combination of a given number of Voltaic 



Elements for obtaining the greatest effect with a given closing 



chcuit 359 



§ 24. The most suitable arrangement of the closing arc for obtaining a 



maximum effect with a given electro-motor.. 364 



§ 25. Comparison of the effects of different Batteries in given cases 367 



§ 26. Rheostats 368 



§ 27. Differential Measurer of Resistance 369 



Section Third. Resistance of Metals and Liquids, Galvanic Polarization 



AND Passivity 371 



§ 28. Introduction. 371 



§ 29. Resistance of metals 371 



§ 30. Dependence of the resistance of metals on temperature 373 



