astronomy, in the shape of 'Observations on the Trigonometrical Tables
of the Brahmins,' and also a masterly collection of 'Theorems on the
Figure of the Earth.' During the course of the last-mentioned year,
his friend Dr. James Hutton died; and Playfair, having undertaken to
draw up a biographical account of him for the Royal Society, was led
to study the doctor's ingenious but crude speculations on the 'Theory
of the Earth,' and afterwards to lend them the assistance of his own
powerful pen, in his 'Illustrations of the Huttonian Theory.' This
work, upon which he bestowed more time and labour than on any of his
other productions, did not appear until 1802; and whatever opinion may
be formed of the truth or soundness of Dr. Hutton's speculations, it is
impossible to doubt that Playfair's illustration of that theory must
always be ranked amongst the most brilliant and powerful productions of
philosophical genius. Its merits have been universally acknowledged,
even by those not convinced by its reasonings, and have extorted, even
from the fastidious critics of France, the acknowledgment that "Mr.
Playfair writes as well as Buffon, and reasons incomparably better."
In 1805 he quitted the chair of mathematics to succeed Professor
Robison in that of natural philosophy. In the contest which ensued
upon the appointment of Leslie as his successor in this chair, he took
a very active part; and amongst the heaviest blows which Leslie's
opponents had to sustain, were those that parted from the hand of
Mr. Playfair. In 1807 he was elected a Fellow of the Royal Society,
to which learned body he very soon afterwards presented his 'Account
of the Lithological Survey of Schehallien;' this was the result of
his investigations during the period of Dr. Maskelyne's visit to
Schehallien, to measure the attraction of that mountain, on which
occasion Playfair shared the shelter of this distinguished astronomer's
tent on the side of the mountain, and contracted with him a friendship
which lasted during the remainder of their lives.
In 1809 he contributed to the 'Edinburgh Transactions' an excellent
paper on 'Solids of the Greatest Attraction,' and in 1812, another,
on the 'Progress of Heat in Spherical Bodies.' In 1814 he published,
in two volumes octavo, for the use of his class, an elementary work
of great value, under the title of 'Outlines of Natural Philosophy.'
About the same time he drew up for the 'Encyclopædia Britannica' an
introductory 'Dissertation on the Progress of Mathematical and Physical
Science,' a treatise distinguished for the soundness of judgment,
beauty of writing, and extent of knowledge displayed in it. In 1815,
Playfair wrote for the Royal Society of Edinburgh a very interesting
memoir of his distinguished predecessor, Dr. Robison. In the course of
the same year he undertook, at the age of sixty-eight, a long journey
through France and Switzerland into Italy, and did not return for a
period of nearly eighteen months, during which time his principal
attention was directed to the mineralogical and geological phenomena
of the different regions which he visited. On his return from this
expedition, he was occupied in drawing up a memoir on the 'Naval
Tactics of Clerk of Eldin,' which was published after his death in the
'Philosophical Transactions.'
Playfair had for several years suffered from a recurrence at different
times of a painful affection of the bladder, which appeared with
increased seventy in the early part of 1819, but was so far got under
as to enable him to complete his course of lectures in the spring. It
returned, however, in a still more distressing form in the summer, and
at last put a period to his life on the 19th of July. Though suffering
great pain during the last part of his confinement, he retained not
only his intellectual faculties quite unimpaired, but also the serenity
and mildness of his spirit, occupying himself until within a few days
of his death in correcting the proof-sheets of the 'Dissertation'
before noticed.
Besides the previously mentioned works, Playfair was a frequent
contributor to the 'Edinburgh Review,' and also wrote the articles
'Æpinus' and 'Physical Astronomy,' in the 'Encyclopædia Britannica.'
Francis Jeffrey, of whose elaborate and elegant memoir the above is but
a brief summary, speaks of Playfair as being "one of the most learned
mathematicians of the age, and among the first, if not the very first,
who introduced the beautiful discoveries of the later Continental
geometers to the knowledge of his countrymen, and gave their just
value and true place in the scheme of European knowledge, to those
important improvements by which the whole aspect of abstract science
has been renovated since the days of our illustrious Newton;" also, "as
possessing in the highest degree all the characteristics both of a fine
and powerful understanding, at once penetrating and vigilant, but more
distinguished perhaps for the caution and sureness of its march than
for the brilliancy or rapidity of its movements; and guided and adorned
through all its progress by the most genuine enthusiasm for all that is
grand, and the justest taste for all that is beautiful."--_Memoir of
John Playfair, by Lord Jeffrey._--_Encyclopædia Britannica._
JOHN RENNIE, F.R.S., L. and E., &c.
Born June 7, 1761. Died October 4, 1821.
John Rennie was born at Phantassie, in the parish of Prestonkirk, in
the county of East Lothian. His father was a highly respectable farmer,
who died in 1766, leaving a widow and nine children, of whom John was
the youngest. He acquired the first rudiments of his education at the
village school, which was situated on the opposite side of a brook.
To cross this at certain seasons of the year it was necessary to
make use of a boat, which was kept at the workshop of Andrew Meikle,
an ingenious mechanic well known in Scotland as the inventor of the
threshing machine. Young Rennie, having thus frequent occasion to pass
through Meikle's workshop, became deeply interested in the various
mechanical operations that were in progress, and a great part of his
leisure and holiday time was spent therein. During the evening he
employed himself in imitating the machines which had particularly
attracted his attention, and when only ten years old succeeded in
constructing a model of a steam-engine, a windmill, and a pile-driving
machine. At twelve years of age he left the Preston school and entered
the service of Mr. Meikle for a space of two years, at the end of which
time, finding that a constant application to manual labour retarded the
progress of his intellectual faculties, he determined to place himself
under the tuition of Mr. Gibson, an eminent mathematical master at
Dunbar. Here Young Rennie attained such proficiency in his studies,
that when, two or three years afterwards, Mr. Gibson was appointed
master to the public academy at Perth, he was able to undertake the
temporary management of the Dunbar school. While at this school he
attracted the especial notice of Mr. David Lock, who, in describing a
visit to Dunbar, makes particular mention of him as one likely to prove
an honour to his country.[29] On leaving Mr. Gibson, Rennie returned
to Mr. Meikle, continuing more or less with that ingenious man for the
next two or three years.[30] His first essay in practical mechanics
was the repairing of a corn mill in his native village, and he erected
two or three others before he had reached the age of eighteen. While
occupied in these works Rennie took care at the same time to attend
to his other studies, managing occasionally to visit Edinburgh, where
he entered himself as a student at the University, and attended the
lectures of Professors Robison and Black. With the former gentleman he
gradually formed an intimate acquaintance, and was by him introduced
to Messrs. Boulton and Watt, of Soho, with whom he remained during
the space of twelve months; it being their wish to have engaged his
services for a longer period, but Rennie, conscious of his own powers,
determined to make the capital the theatre of his future efforts. His
first practical essay at millwright work in England was the rolling
mills at Soho, which were entirely remodelled and rebuilt under his
direction.
In 1784 he established himself in London, and commenced work by the
erection of the Albion Mills near Blackfriars Bridge, Boulton and Watt,
who had the direction of the steam-engines, having, in accordance
with the advice of Professors Robison and Black, entrusted to him
the execution of the millwork. Mr. Watt, in his notes to Professor
Robison's account of the steam-engine, says that "in the construction
of the millwork and machinery, they derived most valuable assistance
from that able mechanician and engineer, Mr. John Rennie, then just
entering into business, who assisted in placing them, and under whose
direction they were executed." He also adds that the machinery, which
used to be made of wood, was here made of cast iron, and considers that
this was the commencement of that system of millwork which has proved
so beneficial to this country. After executing this undertaking, Rennie
was employed on the flour mills at Wandsworth, and the rolling and
triturating mills at the Mint. His mills, and particularly his water
wheels, were regarded as models of perfection, while in all hydraulic
works he was the worthy successor of Smeaton. From this time until his
comparatively early death in 1821, Rennie was constantly employed on
various large and splendid undertakings, among which his bridges occupy
an important place. Of these structures the finest is the Waterloo
Bridge over the Thames, begun in 1809 and finished in 1817. It is built
of Aberdeen granite, and consists of nine equal semi-elliptical arches
of 20 feet span, with a level roadway 45 feet wide from outside to
outside of parapet, which adds greatly to its beauty. This bridge was
opened to the public by the Prince Regent, who offered at the time to
confer upon Mr. Rennie the honour of knighthood; this offer, however,
he declined. London Bridge, which he designed but did not live to
execute, was finished by his sons, Mr. George and Sir John Rennie.
It is built of the finest blue and white granite from Scotland and
Devonshire, and consists of five semi-elliptical arches, two of 130,
two of 140, and the centre one of 152½ ft. span, being perhaps the
largest elliptical arch ever attempted. The beautiful stone bridge
over the Tweed at Kelso, and those at Musselburgh and New Galloway,
were also designed by him. When speaking of the first-named of these
bridges, Mr. Rennie used often playfully to declare, that he considered
himself a benefactor to his country, inasmuch as one of his earliest
public works was to build a bridge across the Tweed! The iron bridges
which he executed are, the one at Boston, over the Witham, with a span
of 100 feet; and the noble bridge at Southwark, over the Thames, begun
in 1815 and opened in 1819. The latter consists of three circular
arches of equal curvature, the centre one having a span of 240, and the
other two of 210 feet. The total weight of iron in the structure was
5780 tons, and the entire cost, including approaches, &c., 800,000_l._
The improvement of harbours and the construction of docks occupied much
of Mr. Rennie's attention, and in these operations his diving-bell
apparatus was of peculiar value. Smeaton was the first who used the
diving-bell effectually for building with stone under water; the
machine he employed for that purpose was, however, very defective, and
could only be used in certain situations. But Rennie, by improvements
in the instrument itself, and in the machinery by which its movements
could be regulated,[31] was enabled to carry on masonry, and the
foundations of sea-walls, piers, and quays, as well under water as
above it. He first employed his apparatus in 1813, in building the
East Pierhead at Ramsgate, the foundations of which were 17 feet
below low water at spring tides. It was afterwards used in founding
the pierheads and outer walls of the harbours at Holyhead, Howth, and
Sheerness, and other works under his direction. Amongst the numerous
wet docks introduced at Liverpool in 1716, and since constructed at
almost all the principal sea-ports in the kingdom, Mr. Rennie executed
the London Docks, and those at Leith, Dublin, Hull, and Greenock,
and also the East and West India Docks, in conjunction with Jessop
and Ralph Walker. He also constructed the harbours of Queensferry,
Berwick, Howth, Holyhead, and that at Kingston, the largest attempted
in this country. At the low water of spring tide, the depth of this
harbour was 26 feet, while the area enclosed amounted to 250 acres. The
breakwater at Plymouth for protecting the Sound from the swell of the
sea was likewise designed by him and Mr. Whitby, and was the first and
largest example of a detached breakwater in this country. One of the
most useful works executed by Mr. Rennie was the drainage of the great
Fen district bordering upon the rivers Trent, Witham, New Welland,
and Ouse, and extending 60 miles in length by 25 in breadth. In the
carrying out of this great work, by which many hundreds of square miles
were rendered productive, and the salubrity of the district improved,
he was assisted by Mr. Telford and his son, Sir John Rennie. The chief
canals of which he was engineer are the Kennet, Avon, Crinan, Rochdale,
and Lancaster. The naval dockyards at Portsmouth, Plymouth, Chatham,
and Sheerness, also attest his skill as an engineer. The latter was
a mere quicksand 40 feet deep, mixed with mud and the wrecks of old
ships; the whole of which was excavated, and a magnificent basin
constructed with a surrounding wall of granite, with which three large
and commodious dry docks communicated. Several magnificent works of
great public utility were proposed to the government by Mr. Rennie but
never executed. The most remarkable of these is his design for a great
naval arsenal on the Thames at Northfleet, intended as a substitute for
the imperfect naval establishments on the river. It was to consist of
six capacious basins, with an area of 600 acres within the walls, and
to comprehend machinery for every operation connected with the naval
science. The estimated cost of this noble plan was eight millions,
which might have amounted to ten or eleven millions, but would even
then have been a measure of economy compared with the vast sums
expended on the old establishments on the Thames and Medway.
Before closing the present brief account of this celebrated engineer's
life and works, his lighthouse on the Bell Rock must not be passed by
without notice. Like the Eddystone, it was built of stone; commenced in
1806, and finished in 1811, it still remains an enduring monument of
the skill of its architect.
Until within a few years of his death Mr. Rennie enjoyed robust health,
but he was cut off in the sixty-first year of his age after a few
days' illness. He was buried in St. Paul's Cathedral, his remains
being interred near to those of Sir Christopher Wren.--_Encyclopædia
Britannica._--_North British Review_, Feb., 1861.--_Mechanics'
Magazine_, September 20 and November 22, 1861.
FRANCIS RONALDS, F.R.S.
Francis Ronalds was born in London, in the year 1788. From a very early
period in life he devoted himself to the advancement of electrical
science, a course he has consistently pursued during a large portion
of his life, which has not yet we are glad to be able to state drawn
to its close. He is the inventor of an electric telegraph, electrical
machine, electrometer, a new mode of electrical insulation, a pendulum
doubler, an electric clock, several meteorological and magnetical
instruments and other mechanical contrivances. The year 1816, however,
marked Mr. Ronald's great achievement in the advancement of electric
telegraphs. During that year he was the first to demonstrate that
they could be practically and unerringly applied to the passage of
messages through a long distance. Well aware of the difficulties
arising from imperfect insulation, which had baffled his predecessors,
Mr. Ronalds secured the success of his apparatus both by employing
better means of insulation than had hitherto been adopted, and also by
making use of a form of apparatus which should of itself be capable
of supplying any loss of electricity which might arise from defects
in the insulation.[32] Mr. Ronalds placed his telegraph wire in glass
tubes surrounded by wooden troughs lined with pitch, which were placed
in a trench dug in his garden at Hammersmith. He also suspended eight
miles of wire by silken cords from a wooden frame erected on his lawn,
through which he was enabled to successfully pass messages except in
wet weather, the cords not being protected from the wet.
Mr. Ronald's peculiar form of apparatus may be thus briefly
described:--At two stations were placed two clocks, with a dial with 20
letters placed on the arbour of the second-hand; in front of each of
these dials was placed a screen with a small orifice cut in it so that,
as the dial revolved, only one letter could be seen at a time. The
clocks were made to go _isochronously_, and were started at the same
instant with the same letter appearing on the dial through the orifices
of each of the screens, both dials, therefore, as they revolved, would
of course continue to show similar letters. This formed the readable
index of his telegraph; means of communication between the two stations
were produced in the following manner:--connected with each end of the
telegraph wire, and placed in front of the clocks, were two pith ball
electrometers, upon which a constant stream of electricity, produced
from an ordinary frictional machine, operated and consequently kept
in a state of divergence, except when a letter on the dial was to be
denoted; the electricity was then partially discharged by breaking the
connection, the pith balls in a measure collapsed, and the distant
observer was thereby informed to note down the letter then visible
through the orifice on the screen. In this way letter after letter
might be denoted and intelligence of any kind conveyed. All that was
absolutely required for the success of Mr. Ronald's telegraph was,
that the clocks should go isochronously _during the time_ intelligence
was being transmitted, for, by a preconcerted arrangement, both clocks
might be easily started at the same letter upon a given signal. The
attention of the distant observer was called by the explosion of gas
by means of an electric spark. In 1823, Mr. Ronalds published a full
description of his telegraph, in a work entitled, 'Descriptions of an
Electrical Telegraph, and of some other Electrical Apparatus.'
In 1825, Mr. Ronalds invented a perspective tracing instrument,
to facilitate drawing from nature or from plans and elevations,
an account of which he published in 1828 in a work entitled,
'Mechanical Perspective.' With this machine he was enabled some
years afterwards (in 1835), assisted by Dr. Blair, to procure exact
perspective projections taken from given noted stations, of the Celtic
remains at Carnac in Brittany. The result of these researches was
published by Mr. Ronalds and Dr. Blair in 1836, and was entitled,
'Sketches at Carnac; or, Notes concerning the present state of the
Celtic Antiquities in that and some of the adjoining Communes.' In
connection with this tracing apparatus, he likewise contrived a
hexipod staff used for a support, and which has been much employed
for the support of instruments requiring great steadiness, such as
telescopes, theodolites, cameras, &c. In the year 1843 he became
the first and honorary director of the Kew Observatory, and while
occupying this office he supplied the observatory with various new
contrivances, for which he received a government reward from the
special service fund, and a small pension from the civil list. The most
considerable of these contrivances were his atmospheric electrical
conductor and its appendages, adopted at the Greenwich, the Madrid,
and the Bombay magnetic observatories; his photo-barograph, and two
photo-thermographs, adopted at the Radcliff observatory, Oxford;
his photo-electrograph, and three photo-magneto-graphs. Besides the
writings above-mentioned, Mr. Ronalds is the author of an article in
the _Philosophical Magazine_ of 1814, entitled, 'On Electro-galvanic
Agency, employed as a moving power, with descriptions of a Galvanic
Clock;' and other articles in the same journal, detailing his
original experiments to illustrate the relations of _quantity_ and
_intensity_ in the electric pile. He also wrote four Reports on the Kew
observatory, which were fully illustrated and printed in the reports of
the British Association for the years 1845-50-51 and 52; and one paper
in the Philosophical Transactions on 'Photographic Self-registering
Meteorological and Magnetical Instruments,' written in 1846 and printed
in the year following. In 1856 Mr. Ronalds published in French, at
Paris, a summary of these reports, with some additions, entitled,
'Descriptions de quelques Instruments Meteorologiques et Magnetiques,'
intended to explain his instruments at the French exhibition.
Mr. Ronalds is now (April 1864) residing at Battle in Sussex, and
during the latter years of life has spent much time and part of his
small pension, in collecting and collating an electric library,
which might be conveniently available for the advancement of his
favourite science, and prove worthy of presentation or bequest to some
British public institution, so as to form the nucleus of one which
might approximate possibly to a complete electrical library.--_From
particulars derived from authentic sources._
COUNT RUMFORD (SIR BENJAMIN THOMPSON), LL.D., V.P.R.S.,
MEMBER OF THE ROYAL INSTITUTE OF FRANCE, ETC.
Born March 26, 1753. Died Aug. 21, 1814.
Benjamin Thompson, the founder of the Royal Institution, and more
generally known by the title of Count Rumford, which he afterwards
acquired, was born at Woburn in Massachussets. His ancestors appear to
have been among the earliest colonists of this district, and in all
probability came originally from England.
Thompson's father died while his son was a mere infant, and two or
three years afterwards his mother married a second husband, Josiah
Pierce, also a resident at Woburn. As soon as young Thompson was able
to learn his letters he was sent to the school of his native town,
kept by a Mr. John Fowle, where he remained until his eleventh year,
when he joined the school of a Mr. Hill at Medford. Here Thompson
made such advances in mathematics and astronomy as to be able to
calculate eclipses. At the age of thirteen he was bound apprentice to
Mr. John Appleby, a respectable merchant in Salem, the second town in
point of size in Massachussets. His occupations with Mr. Appleby were
principally those of a clerk in the counting house, but he appears
to have had sufficient leisure to extend his reading in scientific
subjects, and also to indulge a taste, he began to exhibit, for
designing and engraving. At this time he was likewise occupied with
a contrivance for solving the famous problem of perpetual motion,
but was ultimately made to see the fallacy of his expectations, by
the arguments of an old friend and schoolfellow, Loammi Baldwin,
who induced him to attempt-something more practicable though less
magnificent.
At this period, 1767, the differences between Great Britain and her
American colonies were beginning to assume a serious aspect, and there
ensued such a stagnation of trade at Salem and other towns, that Mr.
Appleby, having no further occasion for the services of a clerk, was
glad to give up to young Thompson his indentures, and allow him to
return to Woburn. For the next two or three years Thompson's course
of life seems to have been wavering and undecided. At one time he
appears to have had thoughts of entering the medical profession,
for he remained during some months under the tuition of Dr. Hay, a
physician in Woburn, and entered zealously upon the study of anatomy
and physiology.