GG J)K. R. ANGUS SMITH ON THE EXAMINATION 



taken the north side, below Dumbarton, instead of the 

 south, on Avhich the vessels sail, the difference would have 

 been greater. 



^^ Leaving Greenock and turning the point, we have 

 a rapid change ; and when off the west of Gourock Bay, 

 at the distance kept by the Liverpool vessels, the amount 

 of oxygen demanded fell to 1*05. Off Wemyss Bay the 

 fall is remarkably low ; but it is not always so, as it depends 

 on tide and wind. The current seems to run down the 

 centre, whilst the ocean-water comes up the coast. The 

 winds and floods may modify this. 



'^ We have to observe a complete change about Gourock 

 or the Cloch, if we keep to the south and east side ; but if 

 we keep to the north, the greatest change is perceptible 

 not far off Helensburgh. 



" This wide space of water reduces the amount of oxygen 

 required to O'ooooi per cent, by weight, or 0*7 grain per 

 100 gallons. 



'' We are now led to ask if the purest state of the water 

 is attained here. We may go further towards the open 

 sea, and find that the amount required falls to 0*000005 

 per cent, by weight, or 0*35 grain per 100 gallons. This 

 is at Arran, where the sea is more extensive, and oxida- 

 tion, even of the peaty matter from the hills, is com- 

 pleted. We observe this to continue till the entrance of 

 the North Atlantic is passed ; and as we : come south, to 

 a narrower channel, the amount of oxidizable matter in- 

 creases and keeps up steadily till we arrive at Liverpool. 

 No specimen was taken nearer than 17 miles from Liver- 

 pool. The point cooooi per cent, oxygen by weight, or 

 0*7 grain per 100 gallons, is an important one to examine. 

 We find that at Dunoon, Innellan, and Holy Loch, this 

 amount may be called permanent. We may ask. Why does 

 it not fall lower ? and is it true that the sewage of Glasgow 

 affects the Firth until we arrive at Lamlash and obtain the 

 number 0*000005 per cent, oxygen by weight, or 0*35 

 grain per 100 gallons? 



"We observe that the amount of purification is remark- 



