544 



Prof. E. Frankland on the Transport of [Feb. 8_, 



In this example a potent cause of the suspension of the zymotic poison 

 in the air was obvious ; but in the many alleged instances of "the propa- 

 gation of typhoid fever by sewer gases, the condition of dispersion is not 

 so evident. Does the flow of sewage in a properly constructed sewer 

 produce sufficient agitation to disperse liquid particles through the air- 

 space of the sewer ? I endeavoured to answer this question by violently 

 agitating a solution of lithic chloride in a glass cylinder 3 inches in dia- 

 meter and 30 inches high, with a wooden rod, and ascertaining whether 

 the atmosphere at the mouth of the cylinder became impregnated with 

 the liquid, by testing it with the flame of a Bunsen burner ; but no trace 

 of lithium could be detected at the mouth of the jar, even after an agita- 

 tion much in excess of what would ordinarily occur in a sewer. Before 

 making this and the subsequent experiments, it was ascertained that no 

 lithic chloride is carried off by aqueous vapour from a saturated solution 

 of this salt at ordinary temperatures, first, by placing a shallow porce- 

 lain basin containing the solution under a bell-jar, and then spectroscopi- 

 cally examining induction-sparks passed through the atmosphere of the 

 bell-jar ; secondly, by burning a mixture of coal-gas and air under a venti- 

 lating tube beneath the bell-jar in such a way as to cause a circulation 

 of air through the jar and then testing the effluent air for lithium as 

 before ; and thirdly, by passing air from a gas-holder over a saturated so- 

 lution of lithic chloride contained in a Woulfe's bottle, and testing the 

 air as it issued from the bottle. 



The results of the experiment in the glass cj'linder render it exceed- 

 ingly improbable that the mere flow of foul liquid through sewers can 

 impregnate the circmnambient air with suspended particles. 



There is, however, another kind of agitation to which sewage is sub- 

 ject that may produce a very different result : I allude to the develop- 

 ment of gases during the processes of fermentation and putrefaction. It- 

 is well known that the bursting of minute bubbles of gas at the surface 

 of an effervescing liquid causes the projection of visible liquid particles 

 into the air to the height of several inches. Such visible particles are 

 seen to fall back again immediately into the liquid ; but it appeared to me 

 not unlikely that other particles, too minute to be seen, might be simul- 

 taneously projected, and, by reason of the smallness of their masses in 

 relation to their sectional areas, might continue suspended in the air for 

 a long time. To ascertain the truth or fallacy of this supposition I made 

 the following experiments. 



A quantity of a strong solution of lithic chloride was placed in a shallow 

 basin and acidulated with hydrochloric acid ; fragments of white marble 

 were then added, and a paper tube 5 inches in diameter and 5 feet high 

 was placed vertically above the basin. So long as the effervescence con- 

 tinued, abundance of particles of lithium were visible in a Bunsen flame 

 held at the upper end of the tube. A tinplate tube 3 inches in diameter 

 and 12 feet Icng was now placed in such a position as to biing one of its 



