28 M. A. F. Simdell on the Electromotive and Thermoelectric 



pies, which, as certainly in the one case as in the other, are the 

 commonly received principles of hydrodynamics. It is therefore 

 logically impossible that any argument against those principles 

 can be drawn from Mr. Moon's reasoning or his results, inas- 

 much as the reasoning has no other basis to stand upon. 



I think it right to add that I have advanced the foregoing 

 argument only as an argumentum ad hominem, intended to show 

 that, even admitting Mr. Moon's premises and his reasoning, no 

 conclusion can be drawn therefrom contradictory to the princi- 

 ples of hydrodynamics. My reason for making this statement 

 here is that I have repeatedly, in this Journal and elsewhere, 

 asserted that I cannot accept either the equation (1) or the 

 equation (4) as a true hydrodynamical equation — not because 

 the principles on which these equations rest are untrue, but be- 

 cause they require to be supplemented. At the same time lean 

 admit the truth and the importance of the equations p =f(p, v) 

 and F(jo, p, u } v, w) = 0, considering them to be necessary for 

 completing the analytical principles of hydrodynamics. Expe- 

 riment can establish the truth of the equation p = a?p only for 

 fluid at rest, whereas by means of these equations it can be shown 

 to be legitimate to assume the same equation to hold good for 

 fluid in motion. 



Having given these explanations I think it needless to pursue 

 the subject at greater length, and accordingly shall decline enter- 

 ing upon any further discussion. 

 Cambridge, December 16, 1873. 



VI. On the Electromotive and Thermoelectric Forces of some 

 Metallic Alloys in contact with Copper. By A. F. Sundell, 

 Docent at the University of Helsingfors*. 



fj^HE remarkable thermoelectric properties of metallic alloys 

 A discovered by the investigations of Seebeck, Rollmann, 

 and other physicists permitted it to be supposed that interesting 

 phenomena must also occur in relation to the power of these 

 bodies, in contact with each other or with unmixed metals, to 

 act in exciting electricity. At the desire of Professor Edlund, 

 therefore, who has determined by a new method the electromo- 

 tive forces of a greater number of metals in contact with copper, 

 and compared them with the thermoelectric forces f, I under- 



* Translated from a separate impression, communicated by the Author, 

 from Poggendorff's Annalen, vol. cxlix. pp. 144-170. 



t Kongl. Svenska Vet. -Akade miens Handlingar, vol. ix. (1871) No. 14; 

 Phil. Mag. Jan. 1871, p. 18; Pogg. Ann. vol. cxliii. pp. 404 & 534. A 

 preliminary investigation will be found in (Efversigt af K.Vet.-Akad. For- 

 handlingar 1870, p. 3 ; Pogg. Ann. vol. cxl. p. 435. 



