542 



Prof. E. Frankland on the Transport of [Feb. 8^ 



II. " On tlie Transport of Solid and Liquid Particles in Sewer 

 Gases/^ By E. Frankland_, F.R.S. Received January Q, 

 1877. 



The suspension of vast aggregate quantities of solid and liquid particles 

 in our atmosphere is the subject of daily remark. Cloud, fog, and smoke 

 consist of such particles, whilst the observations made by the Astronomer 

 Royal for Scotland, on the Peak of Teneriffe, afford evidence of the oc- 

 casional existence of abundance of dust in the air even at great altitudes. 

 I have already mentioned, in connexion with some winter observations in 

 the Alps*, that, by placing the eye in shadow and then looking into the 

 sunshine, I repeatedly saw at a distance of a few feet abundance of 

 snow-crystals floating in the air, when the atmosphere was apparently 

 perfectly clear and cloudless. 



A very large ■ proportion of the suspended particles in the London 

 atmosphere consists of water and other volatile liquid or solid matter, as 

 was, I conceive, proved by Professor Tyndall's observation, that the heat 

 of boiling water is sufficient to dissipate them. That this is the true ex- 

 planation of the disappearance of such particles by the application of a 

 moderate degree of heat, and that it is not caused by the rarefied air from 

 the heated body ascending and leaving behind the suspended matter, as 

 suggested by Tyndallt, is, I think, conclusively proved by the following 

 experiments. 



Two large glass flasks were filled, the one with atmospheric air, the 

 other with hydrogen. Two pieces of cotton-wool moistened, the one 

 with five drops of strong solution of ammonia and the other with eight 

 drops of strong hydrochloric acid, were plunged into each flask and 

 allowed to remain there for a definite period. The time required for the 

 settlement of the suspended particles of ammonic chloride was then 

 noted and was found to be as follows : — 



1. When the pieces of cotton-wool remained in the flasks for two 

 minutes, the ammonic chloride settled dov^Ti in that filled with air in 

 eighteen minutes, and in that filled with hydrogen in ten minutes. 



2. When the pieces of cotton-wool remained in the flasks to the end 

 of the experiment, the settlement in the air-flask required thirty minutes 

 for its completion, whilst that in the hydrogen flask was finished in 

 seventeen minutes. 



It is evident from these results that an atmosphere fourteen times as 



* Proceedings of the Eoyal Society, vol. xxii. p. 317. 



t Proceedings of the Eoyal Institution, vol. vi. p. 4. " What is the explanation ? 

 Simply this. The hot wire rarefied the air in contact with it, but it did not equally 

 lighten the floating matter. The convection-current of pure air, therefore, passed up- 

 wards among the inert jyartioles, dragging them after it right and left, but forming be- 

 tween them an impassable black partition, -sf- -jf -sf Even when its temperature does not 

 exceed that of boiling water, the wire produces a dark ascending current." 



