The Sun.
London, England, 1861-09-05 00:00:00

north-western Hebrides and the west coasts of Sutherland

and Ross, is the oldest rock formation on the British Isles,
it being unknown in England, Wales, or Ireland. It is
well known that the temperature increases as we descend
through the earth's crust, from a certain point near the
surface, at which the temperature is constant. In various
mines, borings, and Artesian wells the temperature has been
found to increase about 1 deg. Fahrenheit for every 60 or
65 feet of descent. In some carefully conducted experi-

ments during the sinking of Dukinfleld Deer Mine—one of
the deepest pits in this country—it was found that a mean
increase of about 1 deg. in 71 feet occurred. If we take the

ratio thus indicated, and assume it to extend to much

greater depths, we should reach at two-anl-a-half miles
from the surface strata at. the temperature of boiling water ;
and at depths of about 50 or 6g miles the temperature
would be sufficient to melt, under the ordinary pressure of
the atmosphere, the hardest rocks. Reasoning from these
facts, it would appear that the mass of the globe, at no
great depth, must be in a fluid state. But this deduction
requires to be modified by other considerations, namely, the
influence of pressure on the fusing point, and the relative
conductivity of the rocks which form the earth's crust.
To solve these questions a series of important experiments
were instituted by Mr. Hopkins, in the prosecution of
which Dr. Joule and myself took part; and after a long
and laborious investigation it was found that the tem-
perature of fluidity increased about 1 deg. Fahrenheit
for every 5001 b. of pressure in the case of spermaceti,
bees'-wax, and other similar substances. However, on
extending these experiments to less compressible sub-
, stances, such as tin and barytes, a similar increase was
not observed. But this series of experiments has been
unavoidably interrupted ; nor is the series on the con-
ductivity of rocks entirely finished. Until they have been
completed by Mr. Hopkins we can only make a partial use
of them in forming an opinion of the thickness of the earth's
solid crust. Judging, however, alone from the greater con-
ductivity of the igneous rocks, we may calculate that the
thickness cannot possibly be less than nearly three times as
great as that calculated on the usual suppositions of the con-
ductive power of the terrestrial mass at enormous depths
being no greater than that of the superficial sedimentary
beds. Other modes of investigation which Mr. Hopkins has
brought to bear on this question appear to lead to the conclu-
sion that the thickness of the earth's crust is much greater
I even than thatabove stated. This would require us to assume
that a part of the heat in the crust is due to superficial and
external rather than central causes. This does not bear
directly against the doctrine of central heat, but shows that
only a part of the increase of temperature observed in
mines and deep wells is due to the outward flow of that
heat. Touching those highly interesting branches of science,
Botany and Zoology, it may be considered presumptuous
in me to offer any remarks. I have, however, not entirely
neglected, in my earlier days, to inform myself of certain
portions of natural history, which cannot but be attractive
to all who delight in the wonderful beauties of natural
objects. How interesting is the organisation of animals and
plants; how admirably adapted to their different functions
and sphere of life. They want nothing, yet have nothing
superfluous. E very organ is adapted perfectly to its func-
tions ; and the researches of Owen, Agassiz, Darwin,
Hooker, Daubeney, Babington, and Jardine fully illustrate
the perfection of the animal and vegetable economy of
nature. Two other important branches of scientific research,
Geography and Ethnology, have for some years been united,
in this association, in one section, and that probably the
most attractive and popular of them all. We are much
indebted to Sir Roderick Murchison, among other members
of the association, for its continued prosperity, and the
high position it has attained in public estimation. The
spirit of enterprise, courage, and perseverance displayed
by our travellers in all parts of the world have been
powerfully stimulated and well supported by the Geo-
graphical Society; and the prominence and rapid publicity
given to discoveries by that body have largely promoted
geographical research. In physical geography the late
Baron von Humboldt has been one of the largest contri-
butors, and we are chiefly indebted to his personal re-
searches and numerous writings for the elevated posi-
tion it now holds among the sciences. To Humboldt
we owe our knowledge of the physical features of Central
and Southern America. To Parry, Sir James Ross, and
Scoresby we are indebted for discoveries in the Arctic
and Antartic regions. Geography has also been advanced
by the first voyage of Franklin down the Copper Mine
River, and along the inhospitable shores of the Northern
Seas, as far as Point Turn Again ; as also by that ill-fated
expedition in search of a North-West passage, followed by
others in search of the unfortunate men who perished in their
attempt to reach those ice-bound regions, so often stimu-
lated by the untiring energy of a high-minded woman. In
addition to these the discoveries of Dr. Livingstone in
Africa have opened to us a wide field of future enterprise
along the banks of the Zambesi and its tributaries. To these
we may add the explorations of Captain Burton in the same
continent, and those also by Captain Spoke and Captain
Grant of a hitherto unknown region, in which it has been
suggested that the White Nile has its source, flowing from
one of two immense lakes, upwards of 300 miles long by 100
broad, and situated at an elevation of 4,000 feet above the
sea. To these remarkable discoveries I ought to add an
honourable mention of the sagacious and perilous explora-
tion of Central and. Northern Australia by Mr. M'Douall
Stuart. Having glanced, however imperfectly, at some of
the most important branches of science which engage the
attention of members of this association, I would now invite
attention to the mechanical sciences, with which I am more
familiarly acquainted. They may be divided into theoreti-
cal mechanics and dynamics, comprising the conditions of
equilibrium and the laws of motion; and applied mechanics,
relating to the construction of machines. I have already
observed that practice and theory are twin sisters, and must
work together to ensure a steady progress in mechanical art.
Let us, then, maintain this union as the best and safest basis
• of national progress, and, moreover, let us recognise it as
one of the distinctive aims of the annual reunions of this
association. During the last century the science of applied
mechanics has made strides which astonish us by their
magnitude; but even these, it may reasonably be hoped, are
but the promise of future and more wonderful enlargements.
I therefore propose to offer a succinct history of these im-
provements, as an instance of the influence of scientific pro-
gress on the wellbeing of society. I shall take in review
the three chief aids which engineering science has afforded
to national progress—namely, canals, steam navigation, and
railways; each of which has promoted an incalculable ex-
tension of the industrial resources of the country. One
hundred years ago the only means for the conveyance of
inland merchandise were the packhorses and waggons on
the then imperfect highways. It was reserved for Brindley
Smeaton and others to introduce a system of canals, which
opened up facilities for an interchange of commodities t a
cheap rate over almost every part of the country. The
impetus given to industrial operations by this new system
of conveyance induced capitalists to embark in trade, in
mining, and in the extension of manufactures in almost
every district. These improvements continued for a
series of years, until the whole country was intersected by
canals requisite to meet the demands of a greatly extended
industry. But canals, however well adapted for the transport
of minerals and merchandise, were less suited for the con-
veyance of passengers. The speed of the canal boats seldom
exceeded from two and a half to three miles an hour, and
in addition to this the projectors of canals sometimes
sought to take an unfair advantage of the Act of Parliament,
which fixed the tariff at so much per ton per mile, by adopt-
ing circuitous routes, under the erroneous impression that
mileage was a consideration of great importance in the suc-
cess of such undertakings. It is in consequence of short-
sighted views and imperfect legislation that we inherit the
numerous curves and distortions of our canal system.
These defects in construction rendered canals almost use-
less for the conveyance of passengers, and la to the im-
provement of the common roads and the system of stage
coaches; so that before the year 1830 the chief public high-
ways of the country had attained a remarkable smoothness
and perfection, and the lightness of our carriages and the
celerity with which they were driven still excite the admi-
ration of those who remember them. These days of an effi-
ciently worked system, which tasked the power and speed
of the horse to the utmost, have now been succeeded by
changes more wonderful than any that previously occurred
in the history of the human race. Scarcely had the canal
system been fully developed when a new means of propul-
sion was adopted—namely, steam. I need not recount to
you the enterprise, skill, and labour that have been exerted
in connexion with steam navigation. You have seen its re-
sults on every river and every sea ; results we owe to the
fruitful minds of Miller, Symington, Fulton, and Henry
Bell, who were the pioneers in the great march of progress.
Viewing the past, with a knowledge of the present and a
prospect of the future, it is difficult to estimate sufficiently
the benefits that have been conferred by this application of
mechanical science to the purposes of navigation. Power,
speed, and certainty of action have been attained on the
most gigantic scale. The celerity with which a modern
steamer, with a thousand tons of merchandise and some
hundreds of human beings on board, cleaves the water and
pursues her course far surpasses the most sanguine expec-
tations of a quarter of a century ago, and indeed almost ri-
vals the speed of the locomotive itself. Previous to 1812 our
intercourse with foreign countries and with our colonial pos •
sessions depended entirely upon the state of the weather.
It was only in favourable seasons that a passage was open,
and we had often to wait days, or even a week, before Dub-
lin could be reached from Holyhead. Now this distance of
63 miles is accomplished in all weathers in little more than
three hours. The passage to America used to occupy six
weeks or two months, now it is accomplished in eight or
nine days. The passage round the Cape to India is reduced
from nearly half a year to less than a third of that time,
while that country may be reached by the overland route in
less than a month. These are a few of the benefits derived
from steam navigation, and as it is yet far from perfect, we
may reasonably calculate on still greater ad vantages in our
intercourse with distant nations. I will not here enter upon
the subject of the numerous improvements which have so
rapidly advanced the progress of this important service.
Suffice it to observe that the paddlewheel system of propul-
sion has maintained its superiority over every other method
yet adopted for tho attainment of speed, as by it the best re-
sults are obtained with the least expenditure of power. In
ships of war the screw is indispensable, on account of the
security it affords to the engines and machinery, from their
position in the hold below the water line, and because of
the facility it offers in the use of sails, when the screw is
raised from its position in the well to a recess in the stern