234 THK FLOATING-MATTER OF THE AIR. 



potash solution, furnishes the basis of this conclusion. 

 Even in a comparatively pure atmosphere success does 

 not in every instance attend the experimenter. At Kew, 

 for example, on the 8th of January, thirteen retort-flasks 

 were charged with infusions of cucumber, melon, beef, 

 and sole. Twelve out of the thirteen remained perfectly 

 limpid, but one of them (a cucumber-flask) became dis- 

 tinctly cloudy, and this one alone refused, when tested, 

 to yield the water-l\ammer sound. With due training, 

 however, success mav be rendered invariable. 



§ 30. Experiments with Turnip-cheese Infusions. 



I am unwilling to omit all reference to experiments 

 which have cost considerable labour, and which, though 

 they have not been repeated and controlled to the extent 

 that I could wish, contribute nevertheless to our know- 

 ledge of the present question. This unwillingness causes 

 me to introduce here, in the briefest manner possible, a 

 reference to a series of experiments made with turaip- 

 cheese infusions, which have been so frequently cited as 

 offering a conspicuous proof of the doctrine of- sponta- 

 neous generation. 



The experiments to which I refer were made in part 

 with closed chambers, and in part with hermetically- 

 sealed retort-flasks. The specific gravity of the infu- 

 sions varied from 1008 to 1012. The cheeses employed 

 were Cheshire, Cheddar, Gloucester, Dutch cheese, 

 American cheese, Eoquefort, and Parmesan, the quantity 

 varying from half a grain to two grains for every ounce 

 of the infusion. The cheese being first well triturated 

 in a mortar, so as to render its particles very minute, 

 was intimately mixed with the infusion, which was then 

 boiled for a few minutes and passed through a filter. 

 The filtered liquid was then introduced into its closed 

 chamber, and boiled there for five minutes. 



