278 Mr. Herschel on certain Motions produced in Fluid [Oct. 



from the positive pole was still sensible : when, however, the 

 zinc formed only a millionth part, no difference could be per- 

 ceived between the alloy and pure mercury. 



35. Lead. — An alloy of 200 parts of mercury and 1 of lead 

 possessed the positive property in perfection. When the pro- 

 portion of mercury was 667 to 1, the rotation was still produced, 

 but was not full and regular. When increased to 1000, a slight, 

 but sensible current, was perceived to radiate from the positive 

 pole to a short distance ; but a proportion of 2000 mercury to 

 1 lead extinguished every trace of motion. 



36. Tin acts also in the same way, and with nearly the same 

 energy, as far as I could judge by the eye. It is certainly much 

 inferior to zinc. 



37. Iron communicates the property in question, though 

 present in such minute quantity as not to be detected by prus- 

 siate of potash. On the other hand,* Copper does not commu- 

 nicate it, though its proportion be increased to such a degree as 

 to give a blue solution in nitric acid, and even to render the 

 mercury quite sluggish.* 



38. Of the other metals I have tried, Antimony is the only 

 one which appears to exert a perceptible action, and this is so 

 slight (never amounting to more than a mere start, or slight 

 convulsion of the surface at the first impression) that I am 

 inclined to attribute it to impurities in the antimony used, espe- 

 cially as this metal stands very low in the scale of electro-posi- 

 tive energy. Bismuth, silver, and gold, though present in 

 considerable quantities in the mercury, impart to it no power of 

 rotation whatever. 



39. This property then of the metals bears an evident relation 

 to their electro-positive energies. It even affords something 

 like a numerical estimate of them ; rude indeed, and liable to a 

 thousand objections, but still not without its value in our 

 present state of complete ignorance on that most interesting of 

 all chemical problems. If it be true, that the whole of chemistry 

 depends on electrical attractions and repulsions, every thing 

 which offers a prospect, however remote, of one day arriving at 

 an exact knowledge of the intensities of these forces, must be 

 regarded as of consequence. It may be objected, that it is 

 only the excess of the electro-positive energy of the alloying 

 metal over that of the mercury, or the alloy over the liquid, that 

 we measure in these experiments, by the quantity of it required 

 to impart a certain appreciable momentum. Yet it is something 

 to have rendered it probable, that this excess in the cases of 

 sodium, zinc, and lead, are in proportions not very remote from 



* The amalgam of iron obtained in one experiment was a white friable solid of a 

 lustre between silver and iron : the mercury being driven oflfby heat, the iron took fire, 

 ■ lowed like a live coal till reduced to the state of black oxide, soluble in muriatic 

 ncirl, haying all its characters. 



