434 NATURAL SCIENCE. June, 1893. 
with the moist copper stage of the microscope proved strongly oligo- 
dynamic after an interval of sixteen days. 
Professor Cramer directed his attention chiefly to the action of 
copper and mercury upon water; he obtained them chemically pure, 
and placed them in vessels, some of which were carefully stoppered 
and full to the brim with neutral distilled water, others were only half 
full, and were supplied with oxygen and carbonic acid. The water 
in both cases became oligodynamic, the latter more powerfully; but 
though, in the former, the air had been carefully excluded, the water 
gave an acid reaction. Zurich water, which was chemically neutral, 
contained very little chalk, but there was enough to cause discoloura- 
tion, as the carbonic acid, which had held the lime in solution, was 
set free and passed over with distillation. Besides this acid, Pro- 
fessor Cramer thinks there might be traces of silicic acid present. 
In addition to the neutralising agents enumerated by Nagel, it 
was found that iron rust was very effective, as also Leptothrix ochvracea, 
an Alga belonging to the Schizophyte rich in ferric hydrate. 
With the various solutions the same effects were produced as 
already recorded; first that of chemical poisoning in the cells when 
much of the deleterious agent was present, followed by the equally 
fatal oligody namic reaction in diluted solutions. At a certain stage 
of dilution, if neutral water were employed, all reaction ceased. 
ANNIE LoRRAIN SMITH. 
