34 NOTE ON THE SO-CALLED SOLUBLE PEROXIDE OF IRON. 
little through each cheek, and is fitted accurately into its position by two keys 
placed under it, and resting on the cheeks, the borings through which correspond 
with its wedge-shape. It is covered with fustian, which gives it a yielding surface 
for the iron plates to press the cloth against whilst being drawn through. By 
these arrangements leakage from the trough is entirely prevented. 
The play of the front plate (6), as has been stated, requires regulating for 
different plasters, and when they are required to be spread of different degrees 
of thickness; this is done by means of two screws (ff) working in nuts (gg) 
which are riveted to the plate; the heads (hh) of these screws work against 
threadless nuts (ZZ) attached to the cheeks (ad). By screwing or unscrewing 
these, the plate can be adjusted to spread any thickness of plaster. It will be 
observed that the screws can prevent the plate falling below any given depth, 
yet allow it to be raised to permit any inequality in the cloth, etc. to pass under 
it and again to resume its position. To assist it to do this, two levers (kk), with 
moveable weights (ZZ) attached, press upon the heads (hh) of the screws, and in¬ 
directly the pressure is exerted upon the plate, or the nuts (ii). For common 
strapping and plasters, which require to be thinly spread, the bolts are un¬ 
screwed so far that the heads of the screws do not. rest on the threadless nuts (ZZ), 
the plate therefore presses without any obstruction on the cloth, and, in addi¬ 
tion to its own weight, pressure is exerted upon it indirectly by the weights 
and levers, as above stated. This plate is nearer the perpendicular than the 
back plate, because the spread-plaster (in) should be drawn through as nearly at 
right angles with it as possible. 
The cloth being placed on a roller (n), which is suspended on two rests (oo), is 
passed through the bottom of the trough, taking with it a layer of the liquefied 
plaster (contained in the trough) as it is drawn off at (m). 
By regulating the front plate with the screws (ff), skins, felt, or other thick 
material can be spread in the same manner as has been described. 
The condition of the plaster, its temperature, and that of the plates suitable 
for spreading, are matters which require careful attention to produce satisfac¬ 
tory results. 
The heating apparatus (p) is a Bunsen’s burner with two branches (qqq), which 
perforate the cheeks at each end. Gas is supplied by means of an india-rubber 
tube. A stopcock regulates its admission through a small tube into the interior 
of the larger tube. Air is admitted to mix with the gas by holes near the 
bottom of this, the quantity being regulated by the usual nozzle. The mixture 
of gas and air is burnt in a row of jets in each branch directed against the 
plates (b and c) ; thus these and the liquefied plaster in the trough are kept at a 
nearly uniform temperature. 
The burner can be detached and fitted into the machine inverted, so that, 
when not in use, the whole occupies but very little space. 
Mr. J. H. Spencer, Southwark Bridge Hoad, constructed the apparatus under 
the direction and supervision of the inventor. 
NOTE ON THE SO-CALLED SOLUBLE PEROXIDE OF IRON. 
BY WALTER G. SMITH, M.B., 
FELLOW OF THE COLL. OF PHYS., ASSIST. PHYS. TO THE ADELAIDE HOSPITAL. 
This compound occurs in small, cubical, reddish-brown crystals, with a purely 
sweet taste, followed by a slight chalybeate flavour. Being desirous to ascer¬ 
tain if the iron were really combined with the sugar in a soluble form, as asserted, 
