343 
been first superheated and then filled to five cubic centi- 
metres with boiling solution. After each testing the pipette 
is immersed for several minutes in boiling distilled water. 
In six days after impregnation with any zymotic water such 
an eprouvette becomes hazy. It need scarcely be added that 
in each experiment a second charged eprouvette must be 
placed beside the impregnated one for comparison. Both 
must be protected from the air by plugs of cotton wool. 
From the most careful and repeated examinations of waters 
known to be zymotic, we have learnt that such waters often 
contain no elements or particles whatever which can be 
detected by the microscope; so that it may be concluded 
that the elements of which the germinal substance of micro- 
zymes consists are of extreme minuteness. It therefore 
appeared ‘to be of great importance to extend our inquiries 
to water which is optically pure, not merely in the sense that 
it contains nothing which can be detected by the microscope, 
but in the much higher sense that when viewed in the electric 
beam by the method employed by Professor Tyndall it shows 
no haze. Unfortunately it is not as yet possible to procure 
such water. Professor Tyndall has, however, been good 
enough to give us the opportunity of testing specimens 
obtained by the fusion of ice which approach the standard 
of optical purity so nearly that the electric beam in passing 
through them displays a blue colour, Of the results of our 
examination of these specimens it is sufficient to state that 
they are as zymotic as many other varieties of water which 
in the beam are seen to be full of light-scattering particles. 
To determine in how far the zymotic properties of water 
are affected by chemical compounds which are believed to 
have the power of arresting the evolution of living forms in 
organic liquids, a series of experiments were made in which 
the zymotic power of water was tested before and after the 
addition of such compounds, the supposed anti-zymotic being 
contained sometimes in the water to be tested, sometimes in 
the test solution. 
XIX.—March 2-10.—1. A quantity of water previously 
ascertained to be zymotic was ozonised by subjecting it to 
the action of air which has passed over fresh and moist phos- 
phorus, the apparatus for this purpose consisting of (a) two 
Woulff’s bottles containing sticks of phosphorus; () a wash- 
ing bottle containing solution of caustic potash; (¢) a flask 
containing the water to be ozonised. Air was made to pass 
slowly through a, d, c in succession, by means of an aspirator, 
for several hour, after which the liquid in ¢, and the air in 
contact with it, reacted strongly on iodide of potassium and 
