I 



in Melbourne. 197 



pretty exactly with that given above ; the differences being 

 less than I have myself found to occur between samples of 

 my own taken at different times. But Mr. Johnson's report, 

 as published, does not give us the precise information we 

 now require. The determinations given afford us no idea 

 of the presence or absence of the noxious products of decom- 

 position, nor of the nature, physical or chemical, of the 

 organic matter. These all-important particulars I now 

 endeavour to supply ; and, although many of the experi- 

 ments were made more than twelve months since, they are 

 still significant. 



Now it must be conceded that, as Mr. Johnson argues, a 

 dead bullock or so would bear a very small proportion to the 

 large volume of water in the reservoir, and the cold infusion 

 of the beef and its products would not of necessity be 

 detectable by the unaided senses, or even, perhaps, by the 

 ordinary chemical tests. And I can hardly help thinking 

 that this rather detracts from the sedative effect which his 

 report might otherwise have on our minds after Mr. 

 Girdlestone's revelation. 



But there are chemical methods which are pursued when 

 the senses cease to give any indication, and when even the 

 processes in common use fail ; and these methods, or some 

 of them, are specially used in cases of this kind, and are 

 found to give satisfactory indications that cannot be obtained 

 in any other way. They ai-e tedious and operose, but leave 

 taste and smell, lead solutions and platinum salts, far behind. 

 Beside these delicate chemical processes, the microscope 

 furnishes evidence of a very remarkable character. Certain 

 organisms, animal and vegetal, inhabit water of different 

 kinds, and containing different kinds of matter in solution 

 or suspension. I have in the former division of this paper 

 referred to some of these. If any matter is introduced 

 which is unfavourable to any of these organisms, they die 

 out and are replaced by others. In some of these cases the 

 change may be metamorphic, in others total substitution by 

 the introduction or development of other germs. Such 

 changes are familiar to those who interest themselves in 

 this branch of science, and have been often observed by 

 myself 



" It may be a law of Nature," says Kenrick,* " that the 

 .altered condition of the elements shall be slowly followed 



* PrimaBval History. 



