130 Mr. Waldie's Investigations connected [No. 2, 



namely, nitric and nitrous acids, and there are nitrogenised substances 

 in progress of decomposition, as well as non-nitrogenous substances, 

 usually called vegetable, carbohydrates, and hydrocarbons more or 

 less oxidised. Reasons have been given in the first paper for not 

 attaching very much importance to the estimation of nitric acid, yet 

 the enquiry is interesting, to account for the destruction of the 

 nitrogenised matter. If the nitrogen is oxidised, it ought to be found 

 as nitric or nitrous acid, unless it be supposed that it escapes in 

 some gaseous form. Time has not permitted me to investigate this 

 subject, but the few trials I have made for the detection of nitric 

 acid have not been at all successful, — possibly it may be for want of 

 sufficient care. On the other hand, the test recommended for nitrous 

 acid, — Price's test by starch, acid, and Iodide of Potassium, at once 

 gives indications of that acid. But unfortunately it equally has given 

 me free indications in the distilled water used, though means have 

 been taken carefully to free the water and all the re-agents employed 

 from it. At present I can give no explanation of these difficulties : 

 the point is reserved for enquiry. 



The most difficult part of the subject is the estimation of the nature 

 of that more fixed portion of the organic matter which has undergone 

 comparatively little change. The determination of the amount of 

 nitrogen in this is one mode of examining it : I have not at present 

 attempted this, as the waters have during the last four months been 

 in the least favourable condition for such examination, and my time 

 has been occupied with other parts of the enquiry. But I can only 

 confirm what was before stated, that the organic matter evidently 

 varies considerably in its nature : that of the rainy season resembles 

 more that contained in tank waters; that of the dry season is more 

 like that contained in sea water. The former evidently contains 

 more matter of vegetable origin, but so far as I have been able to 

 form a judgment, this only partially accounts for the difference. 



But before proceeding to discuss these points, it may be better to 

 have the whole of the data before us, by including the composition of 

 the tank waters as well as of the river water. In the first paper 

 one table exhibited some of the principal characteristics : now, 

 additional information can be given. It will be exhibited by the 

 following tables. 



