‘ 
, 
! 
‘ 
> 
a ea 
carried from one country to the other, or that both countries 
had obtained their standards from a common source. 
But in the heavens we discover by their light, and by their 
light alone, stars so distant from each other that no material 
thing can ever have passed from one to another, and yet this 
ight, which is to us the sole evidence of the existence of these 
distant worlds, tells us also that each of them is built up of mole- 
cules of the same kinds as those which we find onearth. A 
molecule of hydrogen, for example, whether in Sirius or in Arc- 
turus, executes its vibrations in precisely the same time. 
Each molecule, therefore, throughout the universe, bears im- 
pressed on it the stamp of a metric system as distinctly as does 
the metre of the Archives at Paris, or the double royal cubit of 
the Temple of Karnac. ’ 
No theory of evolution can be formed to account for the simi- 
larity of molecules, for evolution necessarily implies continuous 
change, and the molecule is incapable of growth or decay, of 
generation or destruction. 
None of the processes of Nature, since the time when Nature 
began, have produced the slightest difference in the properties of 
any molecule. We are therefore unable to ascribe either the 
existence of the molecules or the identity of their properties to 
the operation of any of the causes which we call natural. 
On the other hand, the exact quality of each molecule to all 
others of the same kind gives it, as Sir John Herschel has well 
said, the essential character of a manufactured article, and pre- 
cludes the idea of its being eternal and self.existent. 
Thus we have been led, along a strictly scientific path, very 
near to the point at which Science must stop. Not that Science 
is debarred from studying the internal mechanism of a mole- 
cule which she cannot take to pieces, any more than from in- 
vestigating an organism which she cannot put together. 
But in tracing back the history of matter Science is arrested 
when she assures herself, on the one hand, that the molecule has 
been made, and on the other that it has not been made by any 
of the processes we call natural. 
Science is incompetent to reason upon the creation of matter 
itself out of nothing. We have reached the utmost limit of our 
thinking faculties when we have admitted that because matter 
cannot be eternal and self-existent it must have been created. 
It is only when we contemplate, not matter in itself, but the 
form in which it actually exists, that our mind finds something 
on which it can lay hold. : 
That matter, as such, should have certain fundamental pro- 
perties—that it should exist in space and be capable of motion, 
that its motion should be persistent, and so on, are truths which 
may, for anything we know, be of the kind which metaphysicians 
call necessary. We may use our knowledge of such truths for 
purposes of deduction but we have no data for speculating as to 
their origin, 
But that there should be exactly so much matter and no more 
in every molecule of hydrogen is a fact of a very different order. 
We haye here a particular distribution of matter—a collocation 
—to use the expression of Dr. Chalmers, of things which we 
have no difficulty in imagining to have been arranged other- 
wise, 
The form and dimensions of the orbits of the planets, for in- 
stance, are not determined by any law of nature, but depend upon 
a particular collocation of matter, The same is the case with 
respect to the size of the earth, from which the standard of what 
is called the metrical system has been derived. But these 
astronomical and terrestrial magnitudes are far inferior in scien- 
tific importance to that most fundamental of all standards which 
forms the base of the molecular system. Natural causes, as 
we know, are at work, which tend to modify, if they do not at 
length destroy, all the arrangements and dimensions of the earth 
and the whole solar system. -But though in the course of ages 
catastrophes have occurred and may yet occur in the heavens, 
though ancient systems may be dissolved and new systems evolved’ 
out of their ruins, the molecules out of which these systems are 
built—the foundation stones of the material universe—remain 
unbroken and unworn. 
They continue this day as they were created, perfect in num- 
ber and measure and weight, and from the ineffaceable characters 
impressed on them we may learn that those aspirations after 
accuracy in measurement, truth in statement, and justice in 
action, which we reckon among our noblest attributes as men, 
are ours because they are essential constituents of the image of 
Him Who in the beginning created, not only the heaven 
and the earth, but the materials of which heaven and earth | 
| Siemens. 
consist. 
NATURE 
Table of Mol.c.l.r D.ta. 
"IE Oye. "oe ala 
Mass ot molecule & ) 
(hydrogen = 1) J Y 16 14 2 
Rank 
I. Velocity (of mean* 
square),metres per 1859 465 497 396 
second at o° C, 
Mean path, tenth- 6 6 82 
Rank metres, 995 ee Ae 379 
- IL, eee 
Collisions in a ) . 
second, (millions) § 17750 7646 9489 9720 
Diameter, tenth- 1 ; f 5 
Rank metre 3 ror 76 8°3 9°3 
IIL. 
Mass, twenty-fifth- 
pried j 46 736 644 OL 
Table of Diffusion : (rete): measure. 
second 
Calculated Observed. 
H&O 0°7086 072145 
H&CO 06519 0°6422 | 
H & CO, 0°5575 0'5558 | Diffusion of matter observed 
O&CO  0'1807 o1802 (by Loschmidt. 
O&CO, 01427 | Oo'1409 
CO & CO, 01386 | o'r4o6 } 
H 12990 | 1°49 } 
oO o'1884 0213 ( Diffcsion of momentum 
(ee) 01748 O'212 \ Graham and Meyer. 
CO, 0°1087 O°L17 j 
Gaidce Boe \igiaton of temperature ab- 
Yeon o'183 | served by Stefan, 
Cane sugar in water 0°00000365 } y, . 
Sa BE ‘ ’ Voit. 
Diffusion in a day 0°3144 j 
Salt in water . . o’00000116 Fick, 
FUEL® 
JX accepting the invitation of the Council of the British 
Association to deliver an address to the operative classes of 
this great industrial district, I felt that I was undertaking no 
easy task. Having to speak on behalf of the Association, and 
in the presence of many of its most distinguished members, 
I am bound to treat my subject scientifically, but I have to bear 
in mind at the same time that [ am addressing myself to men 
unquestionably of good intelligence, but without that scientific 
training which has almost created a language of its own, 
It is no consolation for me to think, that those who have 
taken a similar task upon themselves in former years, have 
admirably succeeded in divesting highly scientific subjects of 
the formalism in which they are habitually clothed. The very 
names of these men—Tyndall, Huxley, Miller, Lubbock, and 
Spottiswoode—are such as to preclude in me all idea of rivalry, 
but I hope to profit by their example, and to remember that 
truth must always be simple, and that it is only where know- 
ledge is imperfect that scientific formule must take the place 
of plain statements. ] : ; 
The subject matter of my discourse is ‘‘ Fuel ;” a matter with 
which every one of us has becomé familiarised from his infancy, 
but which nevertheless is but little understood even by those 
who are most largely interested in its applications ; it involves 
considerations of the highest 2 grioré interest, both from a 
scientific and a practical point of view. ih 
I purpose to arrange my subject under five principal heads :— 
t. What is fuel ? 
2.+Vihence is fuel derived ? 
3. How should fuel be used ? 
4. The coal question of the day. 
5. Wherein consists the fuel of the sun? 
What is fuel?—Some of you may have alrcady said within 
yourselves that it is but wasted time to enlarge upon su-h a 
* Lecture delivered before the British Assocation at Piadford, by Dr. 
