Sept. 10, 1885] 
NATURE 
443 
powder, guns, watches, forks, knitting-needles, horseshoes, bells, 
wood-cutting and copper-engraving, wire-drawing, steel, table 
glass, spectacles, microscopes, glass mirrors backed by amalgams 
of tin and lead, windmills, crushing and saw mills. These im- 
portant manufactures arose from an increased knowledge of facts, 
around which scientific conceptions were slowly concreting. 
Aristotle defines this as science when he says, ‘‘ Art begins 
when, from a great number of experiences, one general concep- 
tion is formed which will embrace all similar cases.” Such con- 
ceptions are formed only when culture developes the human 
mind and compels it to give a rational account of the world in 
which man lives, and of the objects in and around it, as well as 
of the phenomena which govern their action and evolution. 
Though the accumulation of facts is indispensable to the growth 
of science, a thousand facts are of less value to human progress 
than is a single one when it is scientifically comprehended, for 
it then becomes generalised in all similar cases. Isolated facts 
may be viewed as the dust of science. The dust which floats in 
the atmosphere is to the common observer mere incoherent 
matter in a wrong place, while to the man of science it is all- 
important when the rays of heat and light act upon its floating 
particles. It is by them that clouds and rains are influenced ; it 
is by their selective influence on the solar waves that the blue 
of the heavens and the beauteous colours of the sky glorify all 
Nature. So, also, ascertained though isolated facts, forming the 
dust of science, become the reflecting media of the light of 
knowledge, and cause all Nature to assume a new aspect. It is 
with the light of knowledge that we are enabled to question 
Nature through direct experiment. The hypothesis or theory 
which induces us to put the experimental question may be right 
or wrong ; still, predens guestio dimidium scientie est—it is half 
way to knowledge when you know what you have to inquire. 
Davy described hypothesis as the mere scaffolding of science, 
useful to build up true knowledge, but capable of being put up 
or taken down at pleasure. Undoubtedly a theory is only tem- 
porary, and the reason is, as Bacon has said, that the man of 
science ‘‘loveth truth more than his theory.” The changing 
theories which the world despises are the leaves of the tree of 
science drawing nutriment to the parent stems, and enabling it 
to put forth new branches and to produce fruit ; and though the 
leaves fall and decay, the very products of decay nourish the 
roots of the tree and reappear in the new leaves or theories which 
succeed. 
When the questioning of Nature by intelligent experiment has 
raised a system of science, then those men who desire to apply 
it to industrial inventions proceed by the same methods to make 
rapid progress in the arts. They also must have means to 
compel Nature to reveal her secrets. AZneas succeeded in his 
great enterprise by plucking a golden branch from the tree of 
science, Armed with this even dread Charon dared not refuse 
a passage across the Styx ; and the gate of the Elysian fields was 
unbarred when he hung the branch on its portal. Then new 
aspects of Nature were revealed— 
“* Another sun and stars they know 
That shine like ours, but shine below.” 
It is by carrying such a golden branch from the tree of science 
that inventors are able to advance the arts. In illustration of 
how slowly at first and how rapidly afterwards science and its 
applications arise, I will take only two out of thousands of 
examples which lie ready tomy hand. One of the most familiar 
instances is air, for that surely should have been soon understood 
if man’s unaided senses are sufficient for knowledge. Air has 
been under the notice of mankind ever since the first man drew 
his first breath, It meets him at every turn; it fans him with 
gentle breezes, and it buffets him with storms. And yet it is 
certain that this familiar object—air—is very imperfectly under- 
stood up to the present time. We now know by recent re- 
searches that air can be liquefied by pressure and cold ; but as 
a child still looks upon air as nothing, so did man in his early 
state. A vessel filled with air was deemed to be empty. But 
man, as soon as he began to speculate, felt the importance of 
air, and deemed it to be a soul of the world upon which 
the respiration of man and the god-like quality of fire de- 
pended. Yet a really intelligent conception of these two 
essential conditions to man’s existence—respiration and com- 
bustion—was not formed till about a century ago (1775). 
No doubt long before that time there had been abundant 
speculations regarding air. Anaximenes, 548 years before 
Christ, and Diogenes of Apollonia, a century later, studied 
the properties of air so far as their senses would allow 
them ; so, in fact, did Aristotle. Actual scientific experiments 
Were made on air about the year 1100 by a remarkable Saracen, 
Alhazen, who ascertained important truths which enabled 
Galileo, Torricelli, Otto de Guericke, and others at a later 
period to discover laws leading to important practical applica- 
tions. Still there was no intelligent conception as to the com- 
position of air until Priestley in 1774 repeated, with the light of 
science, an empirical observation which Eck de Sulbach had 
made 300 years before upon the union of mercury with an in- 
gredient of air and the decomposition of this compound by heat. 
This experiment now proved that the active element in air is 
oxygen. From that date our knowledge, derived from an in- 
telligent questioning of air by direct experiments, has gone on 
by leaps and bounds. The air, which mainly consists of nitro- 
gen and oxygen, is now known to contain carbonic acid, 
ammonia, nitric acid, ozone, besides hosts of living organisms 
which have a vast influence for good or evil in the economy of 
the world. These micro-organisms, the latest contribution to 
our knowledge of air, perform great analytical functions in 
organic nature, and are the means of converting much of its 
potential energy into actual energy. Through their action on 
dead matter the mutual dependence of plants and animals is 
secured, so that the air becomes at once the grave of organic 
death and the cradle of organic life. No doubt the ancients 
suspected this without being able to prove the dependence. 
Euripides seems to have seen it deductively when he describes 
the results of decay :— 
“ Then that which’springs from earth, to earth returns, 
And that which draws its being from the sky 
Rises again up to the skyey height.” 
The consequences of the progressive discoveries have added 
largely to our knowledge of life, and have given a marvellous 
development to the industrial arts. Combustion and respiration 
govern a wide range of processes. The economical use of fuel, 
the growth of plants, the food of ‘animals, the processes of hus- 
bandry, the maintenance of public health, the origin and cure of 
disease, the production of alcoholic drinks, the processes of 
making vinegar and saltpetre—all these and many other kinds 
of knowledge have been brought under the dominion of law. No 
doubt animals respired, fuel burned, plants grew, sugar fer- 
mented, before we knew how they depended upon air. But as 
the knowledge was empirical it could not be intelligently 
directed. Now all these processes are ranged in order under a 
wise economy of Nature, and can be directed to the utilities of 
life ; for it is true, as Swedenborg says, that human ‘‘ends 
always ascend as Nature descends.” There is scarcely a large 
industry in the world which has not received a mighty impulse 
by the better knowledge of air acquired within a hundred years. 
If I had time I could show still more strikingly the industrial 
advantages which have followed from Cayendish’s discovery of 
the composition of water. I wish that I could have done this, 
because it was Addision who foolishly said, and Paley who as 
unwisely approved the remark, ‘that mankind required to 
know no more about water than the temperature at which it 
froze and boiled, and the mode of making steam.”’ 
When we examine the order of progress in the arts, even 
before they are illumined by science, their improvements seem 
to be the resultants of three conditions : 
(1) The substitution of natural forces for brute animal power, 
as when Hercules used the waters of the Alpheus to cleanse the 
Augean stables; or when a Kamchadal of Eastern Asia, who 
has been three years hollowing out a canoe, finds that he can do 
it in a few hours by fire. 
(2) The economy of time, as when a calendering machine 
produces the same gloss to miles of calico that an African savage 
gives to a few inches by rubbing it with the shell of a snail; or 
the economy of production, as when steel pens, sold when first 
introduced at one shilling apiece, are now sold at a penny per 
dozen ; or when steel rails, lately costing 45/. per ton, can now 
be sold at 52. 
(3) Methods of utilising waste products, or of endowing them 
with properties which render them of increased value to industry, 
as when waste scrap iron and the galls on the oak are converted 
into ink ; or the badly-smelling waste of gasworks is transformed 
into fragrant essences, brilliant dyes, and fertilising manure ; or 
when the effete matter of animals or old bones is changed into 
lucifer-matches. 
All three results are often combined when a single end is 
obtained—at all events, economy of time and production in- 
variably follows when natural forces substitute brute animal 
