434 NATURAL SCIENCE. juNf.iSgi. 



with the moist copper stage of the microscope proved strongly oligo- 

 dynamic after an interval of sixteen days. 



Professor Cramer directed his attention cliiefly 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 Nageli, it 

 was found that iron rust was very effective, as also Leptothrix ochracea, 

 an Alga belonging to the Schizophytae rich in ferric hydrate. 



With the various solutions the Fame 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 oligod) namic reaction in diluted solutions. At a certain stage 

 of dilution, if neutral water were employed, all reaction ceased. 



Annie Lorrain Smith. 



