146 AIR AND LIFE. 



there are as many vertical streaks in the colorless solution as there 

 were particles of dust thrown into it. Each particle's atmosphere of 

 air acts upon the pyrogallic acid, and instantly causes the change of 

 color. The experiment is a very elegant one, and provides a very con- 

 vincing demonstration, and when one thinks of the number of dust 

 particles (either of terrestrial origin or coming from the interplanetary 

 spaces under the form of microscopical meteorites) which uninterrupt- 

 edly pour down on the oceans like some paradoxical dry rain, it is 

 conceivable that the importance of these infinitesimal particles to all 

 aquatic organisms is great. From this point of view, a catastrophe 

 like that of Krakatoa becomes a blessing, and each volcanic outbreak 

 with its concomitant cloud of dust and cinders, which often spreads 

 over hundreds of square miles, and gives forth a soft slow rain of solid 

 l>articles which fall through the air to the water and thence to the 

 underlying abysses, is doubtless a benefit to aquatic organisms. It 

 may seem absurd to speak of the beneficial influence of volcanic catas- 

 trophes upon the denizens of the ocean; the fact is nevertheless incon- 

 testable. Nature abounds in such curious and unexpected interactions. 

 Most of these, as yet, escape us, but some now and then become apparent, 

 and go to show how difficult and complex is the study of life or biology, 

 in its real sense, and how essential is the knowledge of circumstances 

 and surroundings. 



The experiment which has just been referred to suggested to Paul 

 Eegnard the means of measuring, so to speak, the rapidity of the ocean's 

 respiration, the rapidity of diffusion of the aerial gases in water, and 

 especially that of oxygen, which is the most important for organisms. 

 The method is very simple. All that is required is a large glass tube, 

 some 3 yards long, closed at the lower end, placed vertically, and filled 

 with water holding Coupier blue in solution, saturated with hydrosul- 

 phide of soda. This solution, a pale yellow in color, turns blue under 

 the influence of oxygen. The tube thus filled is left to itself and each 

 day an observation is made of the point to which the blue layer has 

 extended. The first day the mere surface only is blue, but by degrees 

 the underlying strata also turn blue, according to the rapidity with 

 which atmospheric oxygen diffuses and is absorbed. Under such cir- 

 cumstances, P. Eegnard noted that in the course of three months oxygen 

 diffused no farther than about a yard from the surface, and the rate of 

 propagation is hardly a centimeter per day. If such is the normal 

 ratio, air penetrates water at the rate of I meters per year, and if, "at 

 the beginning" — of which so much is said, and so little known or know- 

 able — the sea was entirely devoid of oxygeu, no less than a thousand 

 years were required to allow atmospheric oxygen to penetrate to the 

 depth of 4,000 meters, a depth which we all know is not uncommon in 

 the ocean. 



It isthus seen that the respiration of waters is very slow — at least it 

 is very slow so far as diffusion alone is concerned. But, as already 



