THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



FEBRUARY 1852. 



XIII. Reports on the Progress of the Physical Sciences. 

 By John Tyndall, Ph.D. 



[With a Plate.] 



On Thermo-electric Currents, by Prof. Magnus of Berlin*. Experiments 

 of MM. SvANBERGf and FranzJ on Monothermic Electricity^. Ap- 

 plication of the results o/M. Magnus to the solution of certain difficul- 

 ties encountered by M. Regnault. 



EXACTLY thirty years have flown by since the discovery of 

 thermo-electricity by Seebeck in Berlin. Since that time 

 our knowledge of facts in connexion with this subject has been 

 enriched by the labours of Becquerel, Sturgeon, Matteucci, Hen- 

 rici and others ; but our advance towards principles has been 

 slow. Indeed some of the facts at present generally accepted 

 are of so incomprehensible a nature ; the results of various expe- 

 rimenters — and even of the same experimenter at different times 

 — are so perplexing and contradictory, as pressingly to indicate 

 the necessity of further and stricter examination. In the pro- 

 duction of thermo-currents and the determination of their direc- 

 tions, so many hidden influences come into play, that if one 

 subject more than another require the exercise of patience and 

 experimental tact it is this. Until very lately every attempt at 

 progression in this department of inquiry was accompanied by 

 the unpleasant conviction that there was no sure starting-point ; 

 and hence he that would advance had to begin afresh, and 



* Pogg. Ann., vol.lxxxih.p.4<>!). t Comptes Rendits, vol. xxxi. p. 250. 

 X Pog^C- Ann., vol. lxxxiii. p. 374. 



§ I have taken the liberty of applying this term to the electrieity deve- 

 loped by the heating of a single metal. — J. T. 



Phil. May. S. 4. Vol. 3. No. 1G. Feb. 1852. G 



