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446 
Solar Heat.—T have endeavoured to show, inthe early part of 
this lecture, that all available energy upon the earth, excepting the 
tidal wave, is derived from the sun, and that the amount of heat 
radiated year by year, could be measured by the evaporation 
of a layer of water 14 ft. thick, spread over the entire surface, 
which again would be represented by the combustion of a layer 
of coal, covering our entire globe, 1 ft.in thickness, The amount 
of heat radiated away from the sun would be represented by the 
annual combustion of a thickness of coal 17 miles thick, covering 
its entire surface, and it has been a source of wonderment with 
natural philosophers how so prodigious an amount of heat could 
be given off year after year without any appreciable diminution 
of the sun’s heat having become observable. 
Recent researches with the spectroscope, chiefly by Norman 
Lockyer, have thrown much light upon this question. Tt is 
now clearly made out that the sun consists near the surface, 
if not throughout its mass, of gaseous elementary bodies, and 
in a great measure of hydrogen gas, which cannot combine with 
the oxygen present, owing to great elevation of temperature (due 
to the original great compression) which has been estimated at 
from 20,000° to 22,000 Fah. This chemically inert and com- 
paratively dark mass of the sun is surrounded by the phota- 
sphere where the gaseous constituents of the sun rush into com- 
bustion, owing to reduction of temperature in consequence of 
their expansion and of radiation of heat into space ; this photo- 
sphere is surrounded in its turn by the chromosphere, consisting 
of the products of combustion, which, after being cooled down 
through further loss of heat by radiation, sink back, owing to 
their acquired density, towards the centre of the sun, where they 
become again intensely heated through compression and are dis- 
sociated or split up again into their elements at the expense of 
internal solar heat. Great convulsions are thus continually pro- 
duced upon the solar surface, resulting frequently in explosive 
» actions of extraordinary magnitude, when masses of living fire 
are projected a thousand miles or more upward, giving rise to 
the phenomena of sun-spots and of the corona which is visible 
during the total eclipses of the sun. The sun may therefore 
be looked upon in the light of a gigantic gas-furnace, in which 
the same materials of combustion are used over and over again. 
It would be impossible for me at.this late hour to enter deeper 
upon speculations regarding the ‘* regeneration of the sun’s heat 
upon its surface,” which question is replete with scientific and 
also practical interest, because Nature is our safest teacher, and 
in comprehending the great works of our Creator we shall learn 
how to utilise to the best advantage those stores of potential 
energy in the shape of coal which have providentially been 
placed at our disposal. 
COALS AND COAL PLANTS * 
PROF. WILLIAMSON said that his distinguished friend, 
their president, had spoken the truth to a certain 
extent; but at the same time there was in what he 
had said a slight measure of what a particular school would 
call the sxevestio Jalsi. He believed that if a balance of 
account could be struck between them it would be found that 
he (the lecturer) was enormously the gainer from the fact that 
he enjoyed the same name as the president. As far as he 
could arrange the balance it was this—that their president was 
debtor one dinner which he (the lecturer) always contended his 
friend had got because he had received a card of invitation which 
did not belong to him—while, on the other hand, there was an 
item of credit to the extent of all the learning the president dis- 
played at every meeting of the British Association, but for 
which, at least in the North of England, he (Prof. W. C. 
Williamson) was usually credited. Under these circumstances 
he thought it would be seen that instead of his being the loser 
he was in reality an enormous gainer. 
He remembered a distinguished friend of his, a member of the 
House of Commons, telling him that whenever an individual 
rose in that house to speak on a subject on which he was known 
to have written a book, the house speedily became emptied, 
because the members were alarmed at the idea of a speech from 
a man who had an inveterate hobby. He presumed, however, 
that he stood there that night simply because he had a hobby ; 
but he would promise not to ride it too far or inflict it too long 
upon his audience. Furthermore when he remembered how short 
* Abstract of Lecture delivered 
before the British Association, at Bradford 
by Prof. W. C. Williamson, F.R.S, 2 ' 
NATURE 
= ~ 
z ree 
er tht ates. 
| Sept, 25, 1873 
was the time since Prof. Huxley had addressed a Bradford 
audience on the subject of coal, he was somewhat appalled at 
his own boldness in having ventured to deal with a similar 
matter at the present moment. But luckily for him science did 
not stand still, and although so short a time had elapsed since 
Prof. Huxley had delivered the lecture referred to, there was. 
much now to be said on the subject which could not have been 
said then. Still, with the magnifiéent address of Prof. Hi 
within reach, it would not be necessary to detain the auditory 
long on the general theories which were now so widely accepted 
with reference to the origin of cecal. ; 
Prof. Phillips, in his address to the Geological Section on the 
previous morning, had reminded them how short a time it was— 
the period being within his own life-time—since the vegetable 
origin of coal was broadly and openly disputed. It would, how- 
ever, be difficult now to find any one at all enlightened on the 
subject who would venture to dispute that the origin of coal was 
vegetable. In the same way another hypothesis—known by the 
litle of the drift theory—had once been very generally accepted, 
Men who admitted the conclusion that coal had once been a 
mass of vegetable life differed as to the method by which that 
vegetable mass had found its way into its present position, The’ 
majority of the older geologists believed that coal had been 
conveyed into those positions by water—that large qnantities 
of vegetable material had been brought down great rivers like 
the Mississippi or the Ganges, that these vegetable rafts; as they 
might be termed, had accumulated in the estuaries and the 
ocean, and that when they had become thoroughly water-logged, 
they had sunk to the bottom and formed accumulations of vege- 
table elements sufficient to constitute the existing coal-beds, 
Thanks to the labours of a series of indefatigable workers like 
the late Mr. Bowman, Mr, Binney, Sir Wm. Logan, and others, 
we now had a clearerand much more probable conception as to 
what coal originally was, 
It must be understood that although the earth was popularly 
regarded as the type of everything that was stable and immovable, 
this was a very erroneous idea ; for old mother earth was about 
one of the most fickle and inconstant of all the jades with which 
men had deal. She was never still. It happened that at the 
present day there were certain regions, such as the volcanic 
regions, which were always moving upwards, like the more 
aspiring of the youths of Bradford, while there were others, such 
as the coral regions, which were steadily going downward, like 
those less fortunate youths who did not succeed in the race of 
life. So it had been in the olden time. The coal beds ap- 
peared to have accumulated in the latter class of areas—the 
areas of depression—geographical areas in which the earth had 
atendency to sink below the level of the ocean. Upon such 
areas mud and silt had accumulated until the deposit thus formed 
had reached the level of the water, and then came what would 
appear to have been highly necessary as a prelimi to the 
growth of the coal material, namely, a bed of blue mud. It 
was not known why that blue mud was there or whence it 
came, but it was as certain as that garden plants required 
favourable soils for their development, that whatever its cause 
the blue mud was the soil which seemed to have been preferred 
by the great majority of the plants constituting the forests of the 
carboniferous era. In it the minute spores or seeds of the vege- 
tables which afterwards became coal, germinated and struck 
root, until eventually the muddy soil became converted into a 
magnificent and almost tropical forest. As the forest grew the 
spores fell from the trees, the half-dead leaves and decayed 
branches also dropped, and by-and-by the stems themselves 
gave way, and thus was accumulated an immense amount of 
vegetable matter. This, in the progress of time, sank below 
the water level, and more mud being deposited on the top of the 
coal, the new formation in turn underwent the same processes as 
its predecessors, until at length a new forest was formed to share 
the same fate as that which had gone before it. The process 
was repeated again and again, until at length we had an accumu- 
lation of materials, mixtures of the various substances he had 
spoken of, alternating with beds of coal, until we had a vertical - 
thickness of rock varying from three, four, or five, toas much 
as eight or ten thousand feet. 
But while these general truths were accepted with little or no 
reservation, there were one or two points contained in Prof, 
Huxley's lecture upon which he would venture for a moment to 
dwell, In that lecture he properly laid stress upon certain 
minute bodies that were found in the interior of coal. 
[The lecturer here pointed to a diagram representing a vertical 
