Part 4 (1/2)

If on a clear night you direct a telescope to one of the many star-cl.u.s.ters of our northern heavens, you will have presented to the eye as good a diagram as we can at present draw of what we suppose would, under certain circ.u.mstances, be seen in a lump of sugar if we could look into the molecular universe with the same facility with which the telescope penetrates the depths of s.p.a.ce.

Do you tell me that the absurdities of Buffon were wisdom when compared with such wild speculations as these? The criticism is simply what I expected, and I must remind you that, as I intimated at the outset, this conception of modern science is in the transition period of which I then spoke, and, although very familiar to scientific scholars, has not yet been grasped by the popular mind. I can further only add that, wild as it may appear, the idea is the growth of legitimate scientific investigation, and express my conviction that it will soon become as much a part of the popular belief as those grand conceptions of astronomy to which I have referred.

Do you rejoin that we can see the suns in a stellar cl.u.s.ter, but can not even begin to see the molecules? I must again remind you that, in fact, you only see points of light in the field of the telescope, and that your knowledge that these points are immensely distant suns is an inference of astronomical science; and, further, that our knowledge--if I may so call our confident belief--that the lump of sugar is an aggregate of moving molecules is an equally legitimate inference of molecular mechanics, a science which, although so much newer, is as positive a field of study as astronomy. Moreover, sight is not the only avenue to knowledge; and, although our material limitations forbid us to expect that the microscope will ever be able to penetrate the molecular universe, yet we feel a.s.sured that we have been able by strictly experimental methods to weigh molecular ma.s.ses and measure molecular magnitudes with as much accuracy as those of the fixed stars.

Of all forms of matter the gas has the simplest molecular structure, and, as might be antic.i.p.ated, our knowledge of molecular magnitudes is as yet chiefly confined to materials of this cla.s.s. I have given below some of the results which have been obtained in regard to the molecular magnitudes of hydrogen gas, one of the best studied of this cla.s.s of substances; and, although the vast numbers are as inconceivable as are those of astronomy, they can not fail to impress you with the reality of the magnitudes they represent. I take hydrogen gas for my ill.u.s.tration rather than air, because our atmosphere is a mixture of two gases, oxygen and nitrogen, and therefore its condition is less simple than that of a perfectly h.o.m.ogeneous material like hydrogen. The molecular dimensions of other substances, although varying very greatly in their relative values, are of the same order of magnitude as these.[A]

[A] As some of the readers of this volume may be interested to compare these values, we reproduce the ”Table of Molecular Data”

from Professor Clerk Maxwell's lecture on ”Molecules,” delivered before the British a.s.sociation at Bradford, and published in ”Nature,” September 25, 1873.

_Molecular Magnitudes at Standard Temperature and Pressure, 0 C.

and 76 c. m._

-----------------------+-----------+---------+----------+--------- RANK ACCORDING TO

Hydrogen.

Oxygen.

Carbonic

Carbonic ACCURACY OF KNOWLEDGE.

Oxide.

Dioxide.

-----------------------+-----------+---------+----------+--------- RANK I.

Relative ma.s.s

1

16

14

22 Velocity in metres

per second

1,859

465

497

396

RANK II.

Mean path in ten

billionths (10^{-10})

of a metre

965

560

482

379 Collisions each

second--number of

millions

17,750

7,646

9,489

9,720

RANK III.

Diameter in hundred

billionths (10^{-11})

of a metre

58

76

83

93 Ma.s.s in ten million

million million

millionths (10^{-25})

of a gramme