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Dr. Hare’s Description of Voltaic Series, &e. 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. 
n 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. VIL.—Engraving and Description of Voltaic Series, com- 
bining the advantages of the trough of Cruickshank with those 
of the Deflagrator ; by Prof. R. Harz, M.D., &c. &c. 
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 sr plates of zinc, 10 X 12, 
alternating with three of copper. The ee plates of one pair, and the zinc of 
the other being soldered to a common metallic,strip, oe plates of zinc being 
soldered to one strip, the copper to another, each of the last oh strips is 
furnished with a gallows screw GG. Between these screws and those gd Ww, 
(see figure in the text,) a communication is made by jpites or copper ro 
To complete the circuit, it is only necessary, to depress the handle siahed to 
the pulleys, in order to raise the reservoir of diluted sulphuric acid, and thus to 
cause it to act on the plates. 
