272 Dr. Hare’s Electrical Machine, &c. 
As compounds, consisting of a basacigen body, hydrogen and a 
radical, do not, when presented to bases, enter into combination ; but 
are on the contrary, decomposed so as to allow another radical to 
take place of their hydrogen, it is inconsistent with chemical law, as 
stated by Berzelius,* or my definition of acidity, (page 9,) to desig- 
nate them as acids. 
I have called the electro-negative “ protocyanure” of iron of Ber- 
zelius, cyanoferrous acid, because there is “ sesquicyanure” in the 
“ cyanureferrico-potassique” of that author, which by analogy with the 
nomenclature of the oxacids, is entitled to the appellation of cyano- 
ferric acid. 
Art. V.— Description of an Electrical Machine, with a Plate four 
feet in diameter, so constructed as to be above the Operator: 
also of a Battery Discharger employed therewith: and some Ob- 
servations on the Causes of the Diversity in the Length of the 
Sparks erroneously distinguished by the terms Positive and Neg- 
ative; by R. Harz, M. D.,; &c. &e. &c. 
Tue opposite engraving represents a machine with a plate four 
feet in diameter, which I have recently constructed so as to be per- 
manently affixed to the canopy over the table of my lecture room. 
This situation I have found convenient even beyond my expecta- 
tions, as the machine is always at hand, yet never in the way. In 
lecturing, with the aid of a machine on the same level with the lec- 
turer, one of two inconveniences is inevitable. Either the machine 
will occasionally be between him and a portion of the audience, or 
he must be between a portion of the audience and the machine. 
Situated like that which I am about to describe, a machine can nei- 
ther hide the lecturer, nor be hidden by him. With all its power 
at his command, while kept in motion by an assistant, he has no 
part of it to reach or to handle besides the knob and sliding rod of 
the conductor, which are in the most convenient situation. 
The object of this machine being’ to obtain a copious supply of 
electricity for experiments, in which such a supply is requisite, it 
was not deemed necessary to insulate the cushions and the axis, 48 
in the ecteisal plate machine which I employ for experiments re- 
guiting insulation.+ 
* Traite, 4], vol. ii... : 
aman 1888, val. vii, p; 108; or London Phil. Mag. for 1823, rol 
