TRANSACTIONS OF SECTION B. 517 



2. On the Detection by means of the Microphone of Sounds which accompany 

 the Diffusion of Gases through a thin Septum. By W. Chandler 

 Robert's, F.B.S. 



The author pointed out that the passage of a gas through a porous septum 

 was undoubtedly due to molecular motion, and as any facts -which bear on 

 molecular movement are of much importance, he exhibited and described 

 various forms of apparatus, by the aid of which the passage of hydrogen through 

 thin septa of paper and graphite might be studied with the microphone. He indi- 

 cated the several points which appeared to be in favour, as well as those which 

 were against the view that the vibrations of the molecules of the gas could 

 actually be detected, and he stated that further experiments were in progress. 



3. A short Account of Baeyer's Synthesis of Indigo. By Professor J. 

 Emerson Reynolds, M.A., F.G.S. 



4. Dr. Ramsay exhibited Victor Meyer's Apparatus for taking Vapour 

 Densities of Substances with High Boiling Points. 



5. On the Condensation of the Gases hitherto called Permanent. 

 By Professor James Dewar, F.B.S. 



On a Method of Elementary Organic Analysis by a Moist Process. 

 By Professor "Wanklyn and W. J. Cooper. 



7. On some Peculiarities of the Vartry Water, and on the Action of that Water 

 upon Boiler Plates. By Charles R. C. Tichborne, LL.D., Ph.D., 

 F.C.S.- 



The water of the river Vartry, from which we get our supply in Dublin, has 

 been repeatedly analysed, therefore I will not trouble the section with a detail of 

 its composition. It will be sufficient for my purpose to remind the section of its 

 general composition, which may be stated to consist of — 



Organic matter of a peaty nature, 1"6 to 2 grains per gallon. 

 Mineral matter 2£ grains per gallon. 



The mineral matter chiefly consisting of chlorides of the alkalies, and the alkaline 

 earths in equal proportions. 



The hardness is nearly all permanent, as there is but a trace of carbonates 

 present. The point I wish to draw attention to, however, is the presence of nitrates 

 and nitrites. The first are always present, the latter occasionally in the summer 

 and autumn months. They were present when last tried on the 3rd of August. 

 I have never seen any published analysis which mentions the existence of these 

 acidulous radicals. As my object is to determine the condition of the nitrogen 

 salts, and as heat seems to reduce nitrates when occurring in this water, I had re- 

 source to evaporation by the aid of a vacuum and sulphuric acid ; the test I used 

 being the brucia test, an extremely delicate one if properly applied. For my 

 nitrates 1 used a thin starch solution, made with a little dilute glycerine to keep 

 it, and a solution of tartaric acid preserved by a little salicylic acid. The iodide of 



