340 Dr. Schunck on the Phenomena of Fermentation. 



Suppose the two wires to be in contact with each other ; let 

 there be a terrestrial current which induces a current in AB 

 sufficient to cause a deviation d in the galvanometer at F, the 

 same cm-rent will induce a current in C I) which will produce a 

 deviation d' in the galvanometer at F. But since these two cur- 

 rents enter the helix at its opposite ends, d and d' have opposite 

 signs; the total deviation is d—d', a quantity that will generally 

 be small. 



Now by means of the commutator place the battery in circuit, 

 and let the deviation produced by the battery be D ; the in- 

 duced currents remain the same as before ; the total deviation 

 will be J) + d—d'=J) nearly. 



If in practice d—d' could be rendered so small as not to be 

 comparable with D, there would be no need of keeping the ends 

 of the telegraph wires in contact when the battery is out of cir- 

 cuit ; it would be sufficient to insulate them, so as to prevent 

 any extraneous current passing by accident through the wires. 

 If d—d' could not be rendered small enough to be neglected, it 

 would at all events be smaller than d, which is the deviation under 

 the present system. And it would not, I think, be impossible 

 to distinguish the battery signal by a previous arrangement 

 having been made by the operators to send battery signals at 

 constant intervals of time, every 10 seconds for instance, read- 

 ing off immediately before and after the signal was transmitted. 



LII. On the Phcenomena of Fermentation. 

 By E. Schunck, Ph.D., F.R.S. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



THE Cumptes Rendus for 1858 and 1859 contain several 

 communications from M. Pasteur, giving an account of 

 the results obtained by him in an investigation of some of the 

 phsenomena of fermentation. One of the chief discoveries which 

 he announces as resulting fi-om his researches, is that of the for- 

 mation of succinic acid from sugar by fermentation, that acid 

 being, as he states, so constantly produced during the process 

 that it cannot be considered in the light of an accidental product. 

 M. Pasteur seems, however, to be unavrare that the formation of 

 succinic acid during the fermentation of sugar has been observed 

 before. In a paper read before the Manchester Literary aud 

 Philosophical Society in April 1854, and published in the twelfth 

 volume of its 'Memoirs*,' I gave an account of some experi- 



* See also the Philosophical Magazine for September 1854. 



