104 
IMPORTANT discovery BY E. DAVY, F. R. S. 
is varied, acoordins to the fineness of the 
colour we desire to obtain. 
After dyeins; those parts of the cloth in- 
tended to be white, are always, more or less 
tinged with the madder, and much pains are 
necessary to restore their purity. For this 
purpose, boiling with bian, or with soap, 
exposure to light upon the grass, clearing 
with chloride of lime, or other substances, 
which have the property of dissolving or 
destroying this colouring matter, with repeat- 
ed washings in cold water, are all resorted to 
according to circumstances. And several of 
these operations have the additional effect of 
brightening the red, by abstracting a brown- 
ish matter, which always combines with the 
alumina, atthesame time with the red colour- 
ing matter. 
(To he continued.) 
PROGRESS OF SCIENCE. 
By the recent arrivals w^e have received 
our Journals up to January 183G, on Science 
and the Arts. The following' are among the 
interesting articles from which we have 
already made a Selection, and shall make 
others next month. 
Experimental researches into the laws of the 
motion of floating bodies. By J. S. Russell. 
On an economic application of electromagnetic 
forces to manufactui’ing purposes. By Robert 
M allett. 
On a new rotative steam-engine. By John 
Taylor, Esq. 
On the simultaneous vibrations of a cylindri- 
cal tube, and the column of air contained in it. 
By the Rev. James Challis. 
On recent experiments made to protect tin 
plate, &c , from corrosion. By Edmund Davy, 
F. R. S., &c. 
Donisthrope and Raw'son’s improvements in 
the combing of wool, &c. (with an engraving). 
Taylor’s improvements in instruments for mea- 
suring angles and distances, applicable to nau- 
tical purposes (with an engraving). 
Whiteside’s improvements in wheel of steam 
carriages, and in the machinery for propelling 
the same (with an engraving). 
Losh’s improvement in the surface or pattern 
roll of the surface printing machines, and in the 
mode of working them (with an engraving). 
Carter’s improved apparatus for regulating 
the supply of gas to the burners, and for stopping 
oil the same, &c. &o. (with an engraving). 
Leeming’s improvements in water-wheels and 
paddle wheels (with an engraving). 
Potter’s improvements in rendering fabrics 
water proof. 
Hudson on certain machinery applicable in 
block printing on silk, <&c., and on paper (with 
an engraving). 
Boydell on improvements in machinery for 
tracking or towing boats or other vessels (with 
an engraving). 
Schafliautl’s improvements in the manufac- 
turing malleable iron. 
Garner’s improvement in the art of multiply- 
ing certain drawings, &;c. 
ON SOME RECENT EXPERIMENTS 
MADE WITH A VIEW TO PROTECT 
TIN PLAl'E Oa TINNED IRON 
FROhl CORROSION IN SEA-WATER. 
WITH SOME PROBABLE APPLICA- 
TIONS; AND ON THE POWER OF 
ZINC TO PROTECT OTHER METALS 
FROM CORROSION IN THE ATMOS- 
PHERE. BY EDMUND DAVY, F. R. 
S., M. R. 1, A., &c., PROFESSOR OF 
CHEMISTRY TO THE ROYAL DUB^ 
LIN SOCIETY.— If a piece of tin plate is 
exposed in sea-water for a few days, it will 
exhibit an incipient oxidation, which will 
gradually inciea-^e ; the tin will be preserved 
at the expense of the iron, which will be cor- 
roded. But if a small surface of zinc is at- 
tached to a piece of tin plate and immersed in 
sea-water, both the tin and iron will be pre- 
served, whilst the zinc will be oxidated, on 
tlie principle first made known by the late 
Sir H. Davy. 
The author has exposed for nearly eight 
months in sea-water a surface of tin plate 
nailed to a piece of wood by means of tinned 
iron tacks, inseiting between the wood and 
the tin plate a small button of zinc. Under 
these circumstances the tinned plate has re- 
mained clean and free from corrosion ; the 
zinc has of course been corroded. In a com- 
parative experiment, in which a similar piece 
of tin plate was nailed to the same piece of 
wood, and exposed during the sarne period 
to the same quantity of sea-water, without the 
zinc, the edges on two sides of the tin plate 
were quite soft from the corrosion, which had 
extended to about one-eight of an inch. These 
experiments seem worthy of being repeated 
and extended. 
The present demand for tin plate is very 
great; should these statements be confirmed, a 
vast increase in its consumption might he anti- 
cipated. The opinion may be entertained that 
it is practicable to substitute double tin plate 
for sheet copper in covering the bottoms of 
ships, &c., using zinc in small proportions as 
a protector. Such applications would proba- 
bly occasion a saving of nearly three-fourths 
of the present expense of copper sheating. 
It also seems deserving of inquiry, whether 
tin plate vessels, protected by zinc, may not 
be advantageously substituted for copper ves- 
sels in many of our arts and manufactures, 
and even in domestic economy. Although it 
might be presumed, from Sir H. Davy’s 
experiments and observations^, that zinc would 
protect tin plate from corrosion in sea-water, 
the author is not aware that any direct expe- 
riments on the subject have been published. 
Sir H. Davy briefly refers to some obvious 
practical applications of his researches, to the 
preservation of finely divided astronomical 
instruments of steel by iron or zinc ; and that 
* Phtl. Trans., vol. cxiv , foi* 1824; [or, Phil. 
Mag., first series, vol. Ixiv., p. 30, 233 ; vol. Ixv., 
p. 203 .— Edit.] 
