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POPULAR SCIENCE REVIEW. 
and pour on it as much water as will nearly, not quite, cover it. The jar is 
then closed with a cork, and allowed to stand from twelve to eighteen 
hours. At the end of that time, the air in the jar is strongly impregnated 
with ozone. Then, without removing the phosphorus, or water, the engraving 
to be restored is moistened with water, and being rolled up, it is hung in the 
middle of the vessel by a piece of platinum wire, and left at rest. In a little 
time all the parts of the paper not covered by ink are rendered white ; it is 
then removed, and carefully washed with water containing a little soda. 
Our juvenile readers will, doubtless, feel considerable interest in some, 
recent researches by Professor Plateau on the figures assumed by a liquid 
mass wdien the action of gravitation is removed ; not, however, for the sake 
of the curious theoretical conclusions at which he has arrived, although these 
are very remarkable, as for a practical hint which his paper contains, and 
which they will doubtless not be slow to put into practice. 
The Professor had discovered that some of the experiments, which he had 
hitherto been able to try only with great difficulty upon liquid media, inclosed 
in other liquids of the same density, could be readily performed in the air by 
forming the liquids into thin films ; by converting them into “ soap-bubbles,” 
in fact. It was, however, necessary that some more stable kind of bubble 
should be obtained than the one with which we are all familiar, and which 
rarely lasts two minutes ; and after much trouble the following liquid was 
prepared : — One part, by weight of Marseilles soap, previously cut into 
thin shavings, is to be dissolved by heat in forty parts of distilled water, 
and the mixture filtered after cooling. When this is effected, three volumes 
of this liquid are mixed, by violent and continued agitation, with two 
volumes of glycerine ; it is then allowed to stand. The liquid, which is at 
first clear, begins in a short time to grow turbid, and after some days a white 
precipitate will be seen to have risen to the top of the liquid. Draw this oft’ 
with a syphon, and preserve in a stoppered bottle for use. If a bubble be 
blown with this liquid, by means of a common tobacco-pipe, one may readily 
be obtained, four inches in diameter, and if this be supported upon an iron 
ring, one and a half inches across (previously whetted with the glyceric liquid), 
it will remain unbroken for three hours or more in the open air of the room ; 
and for three days even, if protected under a glass-shade. There is a peculiar 
charm in the contemplation of these figures — so sleuder, almost reduced to 
mathematical surfaces — which make their appearance accompanied by the 
most brilliant colours, and which, in spite of their extreme frailness, endure 
for so long a time. 
Analytical chemistry has recently done good service to the poorer inhabitants 
of London. It is known that, scattered about in different parts of the City, 
there are numerous pumps which generally possess a reputation in the 
neighbourhood for more refreshing, sparkling properties than are enjoyed 
by the water companies’ supply. Dr. Letheby, as Medical Officer of Health 
for the City of London, has however dispelled all these pleasing illusions, and 
has disclosed the frightful state of the impurity of these much-admired 
drinking waters. He has been devoting much time to the chemical analysis 
of the water from these wells, and has shown that the coolness of the beverage 
and the briskness of its appearance are dangerous fascinations, for they are 
both derived from organic decay. Dead and decomposing matters have 
