re forms out of oxygen by uniting
it chemically with other primary elements! Thus by uniting it with the
element silica she forms half of the solid crust of the globe; by
uniting it with hydrogen in the proportion of two to one she forms all
the water of the globe. With one atom of nitrogen united chemically with
three atoms of hydrogen she forms ammonia. With one atom of carbon
united with four atoms of hydrogen she spells marsh gas; and so on.
Carbon occurs in inorganic nature in two crystalline forms,--the diamond
and black lead, or graphite,--their physical differences evidently being
the result of their different molecular structure. Graphite is a good
conductor of heat and electricity, and the diamond is not. Carbon in the
organic world, where it plays such an important part, is
non-crystalline. Under the influence of life its molecules are
differently put together, as in sugar, starch, wood, charcoal, etc.
There are also two forms of phosphorus, but not two kinds; the same
atoms are probably united differently in each. The yellow waxy variety
has such an affinity for oxygen that it will burn in water, and it is
poisonous. Bring this variety to a high temperature away from the air,
and its molecular structure seems to change, and we have the red
variety, which is tasteless, odorless, and non-poisonous, and is not
affected by contact with the air. Such is the mystery of chemical
change.

IV

Science has developed methods and implements of incredible delicacy. Its
"microbalance" can estimate "the difference of weight of the order of
the millionth of a milligram." Light travels at the speed of 186,000
miles a second, yet science can follow it with its methods, and finds
that it travels faster with the current of running water than against
it. Science has perfected a thermal instrument by which it can detect
the heat of a lighted candle six miles away, and the warmth of the human
face several miles distant. It has devised a method by which it can
count the particles in the alpha rays of radium that move at a velocity
of twenty thousand kilometers a second, and a method by which, through
the use of a screen of zinc-sulphide, it can see the flashes produced by
the alpha atoms when they strike this screen. It weighs and counts and
calculates the motions of particles of matter so infinitely small that
only the imagination can grasp them. Its theories require it to treat
the ultimate particles into which it resolves ma