176 THE FLOATING-MATTER OF THE AIR. 



were removed in a van from Kew, and shown in the 

 evening of that day to the members of the Eoyal 

 Institution, including many eminent Fellows of the 

 Eoyal Society. The infusions were one and all brilliant, 

 no trace either of turbidity or scum being found associ- 

 ated with any of them. During all my previous efforts 

 (and they had been very numerous) I had never suc- 

 ceeded in saving a single tube of melon-infusion ; here, 

 however, every tube of both chambers was intact. The 

 epidemic was thus localized, the obvious cause of it 

 being the contaminated air of our laboratory, 



A couple of days subsequent to the removal of the 

 chambers from Kew, a single tube of the cucumber- 

 infusion became turbid, its two neighbours in the same 

 chamber remaining intact. Not one of the other tubes, 

 either of melon or cucumber, gave way. They all 

 remained as pellucid in London as they had been at 

 Kew. Their removal from Albemarle Street to the 

 city last year ruined many of our sterilized chambers. 

 I was not therefore prepared to see so little damage 

 done by the transport from Kew. 



It may be remarked, in passing, that this infection 

 of an infusion by mere mechanical shaking is an obvious 

 proof that the contagium is not a gas or vapour, but 

 that it consists of particles capable of being detached 

 from the interior surface of the chamber, and endowed 

 with the power of passing into active life. 



Two other chambers were exposed at the same time 

 in the Jodrell laboratory, the one containing beef- and 

 the other sole- infusion. They are by no means so 

 sensitive as the cucumber and melon, still one of the 

 three beef-tubes broke down, becoming thickly turbid 

 throughout. Eight and left of this tube its two com- 

 panions remained perfectly transparent. As an illustra- 

 tion of the externality of the contagium, the result was 



