r 



EDITORS TABLE, 



493 



EDITOR'S TABLE. 



THE VEXTEXyiAL AXyiVEESAEY OF 

 THE DISCO VERY OF OXYGEy. 



ON the 1st of August, 1874, it will 

 be exactly a hundred years since 

 oxygen g:is was first made known to 

 the world. This discovery is one of 

 the most important ever made in sci- 

 ence, and we commemorate its centen- 

 nial by doing something to mak^ more 

 widely known the character of the 

 illustrious man whose name will be as- 

 sociated with it as long as science is 

 cultivated or civilization continues. 



A hundred years of advancing 

 knowledge has steadily exalted the im- 

 portance of Priestley's discovery. It 

 formed a great epoch in the progress of 

 modern chemistry, and gave a profound 

 clew to the internal constitution of Na- 

 ture. The element first revealed, ex- 

 amined, and described by Priestley, is 

 the most extensive in its distribution, 

 and the most potent in its influence, 

 of all the material constituents of the 

 world. We now know with some defi- 

 niteness the proportions in which oxy- 

 gen exists in the various parts of Na- 

 ture, but the aggregates are so stupen- 

 dous as utterly to baffle the imagination. 

 It exists in the smallest proportion in 

 the atmosphere, forming but one-fifth 

 of its weight. As there are fifteen 

 pounds weight of air on every square 

 inch of the earth's surface, it follows 

 that there are three pounds of oxygen 

 to the same area. By a simple calcu- 

 lation, it therefore turns out that the 

 amount of oxygen in the earth's atmos- 

 phere is one quintillion, one hundred 

 and seventy-eight quadrillions, one hun- 

 dred and fifty-eight trillions of tons — a 

 quantity absolutely inconceivable by the 

 human mind. 



In the world of waters, the scale of 

 proportions is enormously increased, 

 as eight-ninths of the weight of this 



liquid consists of oxygen. The ocean 

 is assumed to cover two-thirds of the 

 earth's surface, and to have an average 

 depth of two miles, which would be 

 sufficient to cover its entire surface to 

 the depth of one mile and one-third. 

 This would give us twenty-seven hun- 

 dred pounds of oxygen for every square 

 inch of the earth, or an amount in the 

 oceans equal to nine hundred atmos- 

 pheres. 



Chemical analysis has also shown 

 us the proportions of oxygen in the va- 

 rious classes of rocks. It forms one- 

 half the weight of siHca, one-third that 

 of alumina, and two-thirds that of lime ; 

 and, as the great bulk of the geological 

 formations are made up of these miner- 

 als, it follows that the entire crust of 

 the globe, so far as it has been explored, 

 with its twenty miles' thickness of 

 stratified rocks and its underlying gran- 

 ites, consists of oxygen to the extent of 

 one-half of its weight. 



If we turn now to the world of life, 

 although the absolute magnitudes are 

 much less, the relative proportions of 

 oxygen are very high, and the grand- 

 eur of its operations is simply amazing. 

 Three-fourths the weight of the entire 

 animal world, and four-fifths the weight 

 of the w^hole vegetable kingdom, con- 

 sist of this element alone. Moreover, 

 the operations of life in both branches 

 are intimately dependent upon its ac- 

 tivity and the rapid changes of which 

 it is the main agent ; while the vege- 

 table kingdom is a grand laboratory, 

 worked by the power of the solar rays 

 to liberate oxygen from its combina- 

 tions, and pour it back into the atmos- 

 phere in a free and active state. The 

 animal kingdom, on the other hand, 

 through all its grades, depends for its 

 existence upon the incessant withdraw- 

 al of oxygen from the air. Each adult 



