122 
Nearly a century since it was noticed that oxygen gas, 
when electrical sparks had been passed through it, acquired 
a peculiar smell and the power of attacking mercury. 
Somewhat later it was found that electrified air possessed 
the property of purifying decomposing animal and vegetable 
matter. In 1826 Dr. John Davy believed this principle 
existed in tlie atmosphere, and proposed tests for its 
detection. 
When residing in Liverpool in the year 1838 I supplied 
some Daniell’s batteries to Mr. T. Spencer. The apparatus 
consisted of a number of cells, in which I had substituted^ 
tliin porous jars, made of ungiazed biscuit ware, to separate 
the two fluids, in place of the bladders, and ox gullets, 
which were very disagreeable in use, and easily destroyed ; 
these porous jars and cells are now in general use, not only 
in Daniell’s, but also in Grove’s, and other batteries in which 
two fluids are employed. 
It was expected that this battery would exhibit consider- 
able power, and an evening was fixed upon to try some 
experiments with it at Mr. Spencer’s house. The parties 
present at these experiments were Mr. Spencer, the late 
Mr. John Wilson (teacher ot chemistry at the Liverpool 
Mechanics’ Institution), Mr. James Kobinson (now of 
Dublin), and myself The first- experiment was the 
decomposition of water. A Faraday’s voltameter, with 
large platinum electrodes, was connected with the battery, 
and the mixed gases, as they were evolved, were collected 
in a glass gas jar, of the capacity of 180 cubic inches. The 
gas jar was filled with water, and placed on the shelf of a 
pneumatic trough ; a bent glass tube from the voltameter 
had its end placed under the open bottom of the jar. When 
the experiment had proceeded for a short time we noticed 
that a white cloud, or vapour, escaped from the bubbles of 
* Page 229. First edition of Elements of IS'atural Philosophy, by Dr. 
Grolding Bird. London, 1839. 
