463. A similar piece of litmus paper, dipped in solution of sulphate of soda _n_, fig. 49, was now supported upon the end of the discharging train _a_, and its extremity brought opposite to a point _p_, connected with the conductor of the machine. After working the machine for a short time, acid was developed at both the corners towards the point, i.e. at both the corners receiving the electricities from the air. Every precaution was taken to prevent this acid from being formed by sparks or brushes passing through the air (322.); and these, with the accompanying general facts, are sufficient to show that the acid was really the result of electro-chemical decomposition (466.). 464. Then a long piece of turmeric paper, large at one end and pointed at the other, was moistened in the saline solution, and immediately connected with the conductor of the machine, so that its pointed extremity was opposite a point upon the discharging train. When the machine was worked, alkali was evolved at that point; and even when the discharging train was removed, and the electricity left to be diffused and carried off altogether by the air, still alkali was evolved where the electricity left the turmeric paper. 465. Arrangements were then made in which no metallic communication with the decomposing matter was allowed, but both poles (if they might now be called by that name) formed of air only. A piece of turmeric paper _a_ fig. 50, and a piece of litmus paper _b_, were dipped in solution of sulphate of soda, put together so as to form one moist pointed conductor, and supported on wax between two needle points, one, _p_, connected by a wire with the conductor of the machine, and the other, _n_, with the discharging train. The interval in each case between the points was about half an inch; the positive point _p_ was opposite the litmus paper; the negative point _n_ opposite the turmeric. The machine was then worked for a time, upon which evidence of decomposition quickly appeared, for the point of the litmus _b_ became reddened from acid evolved there, and the point of the turmeric _a_ red from a similar and simultaneous evolution of alkali. 466. Upon turning the paper conductor round, so that the litmus point should now give off the positive electricity, and the turmeric point receive it, and working the machine for a short time, both the red spots disappeared, and as on continuing the action of the machine no red spot was re-formed at the litmus extremity, it proved that in the first instance (463.) the effect was not due to the action of brushes or mere electric discharges causing the formation of nitric acid from the air (322.).