Di\ Hare's Description of Voltaic Series, &fc. 285 



When hydrogen is employed to analyze the air, with the excep- 

 tion of the quantity requisite to adjust the gage as already explained, 

 it should be the last admitted ; since otherwise it is liable, from its 

 lightness, to pre-occupy the cavity in which the platina wire is sit- 

 uated ; so that some time would be required for its sufficient admix- 

 ture with atmospheric oxygen to constitute a combustible mixture. 



In this mode of operating, when the apparatus is once well ar- 

 ranged, the analysis of the air may be repeated as often as desired, 

 and after any interval of time. 



Art. VII. — Engraving and Description of Voltaic Series, com- 

 hining the advantages of the trough of CruichshanJc with those, 

 of the Deflagrator ; by Prof. R. Hare, M. D., &c. he. 



TO THE EDITOR. 



Dear Sir — In your last number, an abstract was made from Fara- 

 day's researches, agreeably to which my deflagrator, is represented 

 as the best construction, of the voltaic series. It will be recollected, 

 that one principal ground of this alleged superiority is the mechan- 

 ism by which the acid is thrown on or off of the plates, by a partial 

 revolution of the troughs, containing the series and acid, to the ex- 

 tent of one fourth of a circle. 



Subsequently this mechanism, which may be designated as the 

 quadri-rotary mechanism, was applied by me to troughs constructed 

 upon the principle of that of Cruickshank, the pairs being made to 

 exist in a greater degree of proximity than had been previously 

 attempted. It is well known that the Cruickshank pair consists of a 

 plate of zinc and a plate of copper, corresponding in size and shape, 

 placed face to face, and soldered together at one or more of their 

 edges. Pairs' of this kind, slipped into grooves, in a trough so as to 

 be parallel; formed the Cruickshank trough which took place of the 



should contain two galvanic pairs, each consisting of two plates of zinc, 10 X 12, 

 alternating with three of copper. The copper plates of one pair, and the zinc of 

 the other being soldered to a common metallic strip, the other plates of zinc being 

 soldered to one strip, the copper to another, each of the last mentioned strips is 

 furnished with a gallows screw G G. Between these screws and those at W W, 

 (see figure in the text,) a communication is made by leaden or copper rods. 



To complete the circuit, it is only necessary, to depress the handle attached to 

 the pulleys, in order to raise the reservoir of diluted sulphuric acid, and thus to 

 cause it to act on tbcplates. 



