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SEPTEMBE,& 14, 1899 | 
round them things are undergoing that union with oxygen which 
we call oxidation, and that oxidation is the ordinary source of 
heat and light. Let me ask you to picture to yourselves what 
confusion there would be to-morrow, not only in the discussions 
at the sectional meetings of our Association, but in the world 
at large, if it should happen that in the coming night some 
destroying touch should wither up certain tender structures in 
all our brains, and wipe out from our memories all traces of the 
ideas which cluster in our minds around the verbal tokens, 
oxygen and oxidation. How could any of us, not the so-called 
man of science alone, but even the man of business and the man 
of pleasure, go about his ways lacking those ideas? Yet those 
ideas were in 1799 lacking to all but a few. 
Although in the third quarter of the seventeenth century the 
light of truth about oxidation and combustion had flashed out 
in the writings of John Mayow, it came as a flash only, and died 
away as soon asithad come. For the rest of that century, and 
for the greater part of the next, philosophers stumbled about in 
darkness, misled for the most of the time by the phantom con- 
ception which they called phlogiston. It was not until the end 
of the third quarter of the eighteenth century that the new 
light, which has burned steadily ever since, lit up the minds of 
the men of science. The light came at nearly the same time 
from England and from France. Rounding off the sharp corners 
of controversy, and joining, as we may fitly do to-day, the two 
countries as twin bearers of a common crown, we may say that 
we owe the truth to Priestley, to Lavoisier, and Cavendish. If 
it was Priestley who was the first to demonstrate the existence 
of what we now call oxygen, it is to Lavoisier we owe the true 
conception of the nature of oxidation and the clear exposition 
of the full meaning of Priestley’s discovery, while the knowledge 
of the composition of water, the necessary complement of the 
knowledge of oxygen, came to us through Cavendish and, we 
may perhaps add, through Watt. 
The date of Priestley’s discovery of oxygen is 1774, Lavoisier’s 
classic memoir ‘‘ on the nature of the principle which enters into 
combination with metals during calcination ” appeared in 1775, 
and Cavendish’s paper on the composition of water did not see 
the light until 1784. 
During the last quarter of the eighteenth century this new 
idea of oxygen and oxidation was struggling into existence. 
How new was the idea is illustrated by the fact that Lavoisier 
himself at first spoke of that which he was afterwards, namely 
in 1778, led to call oxygen, the name by which it has since been 
known, as ‘‘the principle which enters into combination.” 
What difficulties its acceptance met with is illustrated by the 
fact that Priestley himself refused to the end of his life to grasp 
the true bearings of the discovery which he had made. In the 
year 1799 the knowledge of oxygen, of the nature of water and 
of air, and indeed the true conception of chemical composition 
and chemical change, was hardly more than beginning to be, 
and the century had to pass wholly away before the next great 
chemical idea, which we know by the name of the Atomic 
Theory of John Dalton, was made known. We have only to 
read the scientific literature of the time to recognise that a truth 
which is now not only woven as a master-thread into all our 
scientific conceptions, but even enters largely into the everyday 
talk and thoughts of educated people, was a hundred years ago 
struggling into existence among the philosophers themselves. 
It was all but absolutely unknown to the large world outside 
those select few. 
If there be one word of science which is writ large on the life 
of the present time, it is the word ‘‘electricity’’; it is, I take it, 
writ larger than any other word. The knowledge which it de- 
notes has carried its practical results far and wide into our daily 
life, while the theoretical conceptions which it signifies pierce 
deep into the nature of things. We are to-day proud, and 
justly proud, both of the material triumphs and of the intel- 
lectual gains which it has brought us, and we are full of even 
larger hopes of it in the future. 
At what time did this bright child of the nineteenth century 
have its birth ? 
He who listened to the small group of philosophers of Dover, 
who in 1799 might have discoursed of natural knowledge, 
would perhaps have heard much of electric machines, of electric 
sparks, of the electric fluid, and even of positive and negative 
electricity ; for frictional electricity had long been known and 
even carefully studied. Probably one or more of the group, 
dwelling on the observations which Galvani, an Italian, had 
NO. 1559, VOL. 60] 
NATURE 
405 
made known some twenty years before, developed views on the 
connection of electricity with the phenomena of living bodies. 
Possibly one of them was exciting the rest by telling how he had 
just heard that a professor at Pavia, one Volta, had discovered 
that electricity could be produced not only by rubbing together 
particular bodies, but by the simple contact of two metals, and 
had thereby explained Galvani’s remarkable results. For, 
indeed, as we shall hear from Prof. Fleming, it was in that 
very year, 1799, that electricity as we now know it took its 
birth. It was then that Volta brought to light the apparently 
simple truths out of which so much has sprung. The world, it 
is true, had to wait for yet some twenty years before both the 
practical and the theoretic worth of Volta’s discovery became 
truly pregnant, under the fertilising influence of another dis- 
covery. The loadstone and magnetic virtues had, like the 
electrifying power of rubbed amber, long been an old story. 
But, save for the compass, not much had come from it. And 
even Volta’s discovery might have long remained relatively 
barren had it been left to itself. When, however, in 1819, 
Oersted made known his remarkable observations on the relations 
of electricity to magnetism, he made the contact needed for the 
flow of a new current of ideas. And it is perhaps not too much 
to say that those ideas, developing during the years of the rest 
of the century with an ever-accelerating swiftness, have wholly 
changed man’s material relations to the circumstances of life, 
and at the same time carried him far in his knowledge of the 
nature of things. 
Of all the various branches of science, none perhaps is to-day, 
none for these many years past has been, so well known to, 
even if not understanded by, most people as that of geology. 
Its practical lessons have brought wealth to many ; its fairy 
tales have brought delight to more; and round it hovers the 
charm of danger, for the conclusions to which it leads touch on 
the nature of man’s beginning. 
In 1799 the science of geology, as we know it, was struggling 
into birth. There had been from of old cosmogonies, theories 
as to how the world had taken shape out of primzeval chaos. In 
that fresh spirit which marked the zealous search after natural 
knowledge pursued in the middle and latter part of the seven- 
teenth century, the brilliant Stenson, in Italy, and Hooke, in 
our own country, had laid hold of some of the problems pre- 
sented by fossil remains; and Woodward, with others, had 
laboured in the same field. In the eighteenth century, especi- 
ally in its latter half, men’s minds were busy about the physical 
agencies determining or modifying the features of the earth’s 
crust ; water and fire, subsidence from a primzeval ocean and 
transformation by outbursts of the central heat, Neptune and 
Pluto, were being appealed to, by Werner on the one hand, and 
by Desmarest on the other, in explanation of the earth’s phe- 
nomena. The way was being prepared, theories and views were 
abundant, and many sound observations had been made; and 
yet the science of geology, properly so called, the exact and 
proved knowledge of the successive phases of the world’s life, 
may be said to date from the closing years of the eighteenth 
century. 
In 1873 James Hutton put forward in a brief memoir his 
‘*Theory of the Earth,” which in 1795, two years before his 
death, he expanded into a book ; but his ideas failed to lay hold 
of men’s minds until the century had passed away, when in 
1802 they found an able expositor in John Playfair. The very 
same year that Hutton published his theory, Cuvier came to 
Paris and almost forthwith began, with Brongniart, his immortal 
researches into the fossils of Paris and its neighbourhood. And 
four years later, in the year 1799 itself, William Smith’s tabular 
list of strata and fossils saw the light. It is, I believe, not too 
much to-say that out of these geology, as we now know it, 
sprang. It was thus in the closing years of the eighteenth 
century that was begun the work which the nineteenth century 
has carried forward to such great results. But at that time only 
the select few had grasped the truth, and even they only the 
beginning of it. Outside a narrow circle the thoughts, even of 
the educated, about the history of the globe were bounded by 
the story of the Deluge—though the story was often told in a 
strange fashion—or were guided by fantastic views of the plastic 
forces of a sportive nature. 
In another branch of science, in that which deals with the 
problems presented by living beings, the thoughts of men in 
1799 were also very difterent from the thoughts of men to-day. 
