64 
ANOTHER PLAN FOR PROPELLING STEAM VESSELS. 
substitute a buff. This it does, by depriving 
the manganese of oxygen, and thus rendering 
it soluble; (the manganese is made soluble 
by conversion into chloride of manganese) 
while the protochloride of iron, being con- 
verted into perchloride, deposites peroxide of 
iron on the cloth, which produces the charac- 
teristic buff ox orange colours of that oxide. 
SULPHATE OF IRON is used in a vari- 
ety of ways. It deoxidizes the indigp in the in- 
digo vat, and renders it soluble in lime-water. 
It produces gold, bujf, 8fc. colours, and makes 
a good chemical black with logwood. 
4. PROTOCHLORIDE OF TIN, when 
applied to cloth dyed brown by the sesqui- 
oxide of manganese, immediately deoxidizes it, 
discharges the colour, and leaves the part 
white. Ifit be mixed with Brazil wood, or 
cochineal, it discharges the manganese, but 
leaves a pink. When mixed with logwood, 
it leaver a purple ; and when with Prussian 
blue, a blue. 
To produce a yellow upon manganese 
brown, chloride of tin is mixed with sulphate 
of lead. This mixture thickened with roasted 
starch, is printed on the manganese brown. 
As soon as it is dry, the manganese being re- 
duced to the state of chloride may be washed 
off; but the sulphate of lead adheres to the 
cloth, in consequence of an affinity between 
them. The cloth being now limed, and pas- 
sed through a solution of bichromate of potash, 
those parts which contain the oxide of lead are 
dyed a beautiful yellow. 
CHLORIDE OF TIN is capable also of 
removing peroxide of iron from cloth, by re- 
ducing it to chloride, as it does the sesqui- 
oxide of manganese. For this purpose it is 
sometimes printed on a deep colour, com- 
posed of peroxide of iron and quercition yel- 
low. The protochloride of iron is formed and 
washed away, while the oxide of tin remaining, 
constitutes a mordant for the quercitron. Thus 
the parts to which the tin was applied become 
yellow. 
PROTOCHLORIDE OF TIN is also 
employed occasionally, to discharge the 
orange, consisting of dichromate of lead from 
the cloth. This it does by reducing the chro- 
mic acid to protoxide. But as the green oxide 
of chromium still continues fixed, the dis- 
charged parts do not assume a good white 
colour. But this does not much affect the 
blue and purple colours substituted for the 
orange, by mixing the tin with Prussian-blue, 
or with logwood. 
When protochloride of tin is decomposed by 
carbonate of soda, protoxide of tin is obtained. 
This protoxide is used along with potash, to 
render indigo soluble. The protoxide 
deoxidizes the indigo, and the potash dis- 
solves the yellow base. It is then applied to 
the cloth in the way that will be explained 
afterwards. 
PLAN FOR PROPELLING STEAM 
VESSELS BY THE RETROACTIVE 
FORCE OF A COLUMN OF AIR. 
I> C B 
Str,— T he above sketch represents apian 
for propelling steam -vessels by a powerful 
current of air ejected from the stern of the 
vessel. Water has been tried in a variety of 
ways to effect a similar object, but I am not 
aware of any trial having been made similar 
to the plan proposed. 
A is the cylinder of the air-pump, with 
three inverted steam cylinders on tlie top, 
marked BCD. The piston rods of the in- 
verted cylinders work the plunger of the air- 
pump, and are attached to it at equal dis- 
tances from the centre, and at equal distances 
from each other. The cylinder of the air- 
pump being 10 feet diameter, it is presumed 
that three steam-cylinders so placed would 
be a better arrangement than with one in the 
centre, if even equal to the three in capacity. 
E, an air-vessel, which the air is forced into 
at the passages/ g, alternately, with each 
stroke of the pump. Those passages have 
valves to prevent the air returning into the 
cylinder of the air-pump. 
H, a cast-iron pipe running from the prow 
to the stern of the vessels, and open at both 
ends to the w’ater. There are two cocks or 
valves to this pipe, one on each side of the 
air-vessel. When the air is blowing off to 
propel the vessel forward; the lever K of the 
hand-gear is in the situation represented in 
the figure ; when the lever is raised a little 
higher, the air will rush out at both ends of 
the pipe H, and neutralize the propelling 
force, and if raised a little more, it will be 
discharged at the prow of the vessel only. 
That a power of starting, stopping, and back- 
ing the vessel, may be thus gained, is obvi- 
ous. 
If we suppose the air discharged by the 
pump to be condensed to one-fourth of its 
original volume, and the cylinder of the air- 
pump to be 10 feet diameter, with a 6 feet 
stroke, making 18 strokes per minute, about. 
4,000 cubical feet of air would be discharged 
every minute from the stern of the vessel. 
Question . — What would the probable result 
of such an experiment be, as respects the 
velocity of the vessel so propelled, to the 
power expended, when compared with pad- 
dle-wheels ? I am. Sir, 
Yourverv obedient servant, 
April 24t/i, 1835-. ' J. W. 
[Mech, Mag. 1835. 
(To be continued. ) 
