232 THE FLOATING-MATTER OF THE AIR. 



For ten days of the splendid summer with which we 

 were favoured during a portion of last July, these flasks 

 were exposed daily to the sunlight upon the roof of the 

 Bel Alp hotel. The sky during many of these days was 

 of a deep and cloudless blue ; and certainly in London 

 the actinic rays never approached the power of those 

 here brought to bear upon the infusions. The tempera- 

 ture for many hours of each day was about 120° Fahr. 

 Every evening, when the thermometer had fallen to 

 about 70°, the flasks were removed and suspended above 

 the kitchen-range of the hotel, the temperature gene- 

 rally varying throughout the night from 70° to 80° 

 Fahr. Such variations of temperature, it may be re- 

 marked, are deemed favourable to spontaneous genera- 

 tion. 



After the sunny weather had disappeared, the flasks 

 were allowed to remain for three weeks suspended in 

 the kitchen, with occasional exposures to the sun ; the 

 average temperature of the kitchen where the flasks 

 were hung was about 90° F. The result of the observa- 

 tions was that not one of these forty-five flasks yielded 

 the slightest evidence of spontaneous generation. From 

 first to last they all continued as limpid as distilled 

 water. 



The sealed ends of these flasks were afterwards nipped 

 off under various circumstances, some on the Sparren- 

 horn, some on the glacier, some in the Massa Gorge, 

 some amid the hair of my own head, and some in the 

 rooms of the hotel. Many of them, moreover, were 

 infected with water of various kinds — spring-water, lake- 

 water, and glacier-water. It is not my object to give 

 a detailed account of these experiments, but simply to 

 say that it was not lack of nutritive power on the part 

 of the infusions which prevented the appearance of or- 

 ganisms in the first instance ; for when brought into 



