292 THE FLOATING-MATTER OF THE AIR. 



meter, until the canal is completely blocked up. The 

 second pair of tongs with the fragment of severed neck 

 being withdrawn, the flask, with its contents diminished 

 by evaporation, is lifted from the oil-bath perfectly 

 sealed hermetically. 



Sixty such flasks filled, boiled, and sealed in the 

 manner described, and containing strong infusions of 

 beef, mutton, turnip, and cucumber, are carefully packed 

 in sawdust, and transported to the Alps. Thither, to 

 an elevation of about 7,000 feet above the sea, I invite 

 my co-inquirer to accompany me. It is the month of 

 July, and the weather is favourable to putrefaction. 

 We open our box at the Bel Alp, and count out fifty- 

 four flasks, with their liquids as clear as filtered drink- 

 ing water. In six flasks, however, the infusion is found 

 muddy. We closely examine these, and discover that 

 every one of them has had its fragile end broken off in 

 the transit from London. Air has entered the flasks, 

 and the observed muddiness is the result. My colleague 

 knows as well as I do what this means. Examined with 

 a pocket-lens, or even with a microscope of insufficient 

 power, nothing living is seen in the muddy liquid ; but 

 regarded with a magnifying power of a thousand diameters 

 or so, what an astonishing appearance does it present ! 

 Leeuwenhoek estimated the population of a single drop 

 of stagnant water at 500,000,000 : probably the popu- 

 lation of a drop of our turbid infusion would be this 

 many times multiplied. The field of the microscope 

 is crowded with organisms, some wabbling slowly, others 

 shooting rapidly across the microscopic field. They 

 dart hither and thither like a rain of minute projectiles ; 

 they pirouette and spin so quickly round, that th(3 

 retention of the retinal impression transforms the little 

 living rod into a twirling wheel. And yet the most 

 celebrated naturalists tells us they are vegetables. 



