友情提示:如果本网页打开太慢或显示不完整,请尝试鼠标右键“刷新”本网页!
memoir of fleeming jenkin-第33部分
快捷操作: 按键盘上方向键 ← 或 → 可快速上下翻页 按键盘上的 Enter 键可回到本书目录页 按键盘上方向键 ↑ 可回到本页顶部! 如果本书没有阅读完,想下次继续接着阅读,可使用上方 "收藏到我的浏览器" 功能 和 "加入书签" 功能!
which had overtaken his mother; others shared the fear。 In the
changed life now made for his family; the elders dead; the sons
going from home upon their education; even their tried domestic
(Mrs。 Alice Dunns) leaving the house after twenty…two years of
service; it was not unnatural that he should return to dreams of
Italy。 He and his wife were to go (as he told me) on 'a real
honeymoon tour。' He had not been alone with his wife 'to speak
of;' he added; since the birth of his children。 But now he was to
enjoy the society of her to whom he wrote; in these last days; that
she was his 'Heaven on earth。' Now he was to revisit Italy; and
see all the pictures and the buildings and the scenes that he
admired so warmly; and lay aside for a time the irritations of his
strenuous activity。 Nor was this all。 A trifling operation was to
restore his former lightness of foot; and it was a renovated youth
that was to set forth upon this re‰nacted honeymoon。
The operation was performed; it was of a trifling character; it
seemed to go well; no fear was entertained; and his wife was
reading aloud to him as he lay in bed; when she perceived him to
wander in his mind。 It is doubtful if he ever recovered a sure
grasp upon the things of life; and he was still unconscious when he
passed away; June the twelfth; 1885; in the fifty…third year of his
age。 He passed; but something in his gallant vitality had
impressed itself upon his friends; and still impresses。 Not from
one or two only; but from many; I hear the same tale of how the
imagination refuses to accept our loss and instinctively looks for
his reappearing; and how memory retains his voice and image like
things of yesterday。 Others; the well…beloved too; die and are
progressively forgotten; two years have passed since Fleeming was
laid to rest beside his father; his mother; and his Uncle John; and
the thought and the look of our friend still haunt us。
APPENDIX。
NOTE ON THE CONTRIBUTIONS OF FLEEMING JENKIN TO ELECTRICAL AND
ENGINEERING SCIENCE。 BY SIR WILLIAM THOMSON; F。R。S。; LL D。; ETC。;
ETC。
IN the beginning of the year 1859 my former colleague (the first
British University Professor of Engineering); Lewis Gordon; at that
time deeply engaged in the then new work of cable making and cable
laying; came to Glasgow to see apparatus for testing submarine
cables and signalling through them; which I had been preparing for
practical use on the first Atlantic cable; and which had actually
done service upon it; during the six weeks of its successful
working between Valencia and Newfoundland。 As soon as he had seen
something of what I had in hand; he said to me; 'I would like to
show this to a young man of remarkable ability; at present engaged
in our works at Birkenhead。' Fleeming Jenkin was accordingly
telegraphed for; and appeared next morning in Glasgow。 He remained
for a week; spending the whole day in my class…room and laboratory;
and thus pleasantly began our lifelong acquaintance。 I was much
struck; not only with his brightness and ability; but with his
resolution to understand everything spoken of; to see if possible
thoroughly through every difficult question; and (no if about
this!) to slur over nothing。 I soon found that thoroughness of
honesty was as strongly engrained in the scientific as in the moral
side of his character。
In the first week of our acquaintance; the electric telegraph and;
particularly; submarine cables; and the methods; machines; and
instruments for laying; testing; and using them; formed naturally
the chief subject of our conversations and discussions; as it was
in fact the practical object of Jenkin's visit to me in Glasgow;
but not much of the week had passed before I found him remarkably
interested in science generally; and full of intelligent eagerness
on many particular questions of dynamics and physics。 When he
returned from Glasgow to Birkenhead a correspondence commenced
between us; which was continued without intermission up to the last
days of his life。 It commenced with a well…sustained fire of
letters on each side about the physical qualities of submarine
cables; and the practical results attainable in the way of rapid
signalling through them。 Jenkin used excellently the valuable
opportunities for experiment allowed him by Newall; and his partner
Lewis Gordon; at their Birkenhead factory。 Thus he began definite
scientific investigation of the copper resistance of the conductor;
and the insulating resistance and specific inductive capacity of
its gutta…percha coating; in the factory; in various stages of
manufacture; and he was the very first to introduce systematically
into practice the grand system of absolute measurement founded in
Germany by Gauss and Weber。 The immense value of this step; if
only in respect to the electric telegraph; is amply appreciated by
all who remember or who have read something of the history of
submarine telegraphy; but it can scarcely be known generally how
much it is due to Jenkin。
Looking to the article 'Telegraph (Electric)' in the last volume of
the old edition of the 'Encyclopaedia Britannica;' which was
published about the year 1861; we find on record that Jenkin's
measurements in absolute units of the specific resistance of pure
gutta…percha; and of the gutta…percha with Chatterton's compound
constituting the insulation of the Red Sea cable of 1859; are given
as the only results in the way of absolute measurements of the
electric resistance of an insulating material which had then been
made。 These remarks are prefaced in the 'Encyclopaedia' article by
the following statement: 'No telegraphic testing ought in future
to be accepted in any department of telegraphic business which has
not this definite character; although it is only within the last
year that convenient instruments for working; in absolute measure;
have been introduced at all; and the whole system of absolute
measure is still almost unknown to practical electricians。'
A particular result of great importance in respect to testing is
referred to as follows in the 'Encyclopaedia' article: 'The
importance of having results thus stated in absolute measure is
illustrated by the circumstance; that the writer has been able at
once to compare them; in the manner stated in a preceding
paragraph; with his own previous deductions from the testings of
the Atlantic cable during its manufacture in 1857; and with Weber's
measurements of the specific resistance of copper。' It has now
become universally adapted … first of all in England; twenty…two
years later by Germany; the country of its birth; and by France and
Italy; and all the other countries of Europe and America …
practically the whole scientific world … at the Electrical Congress
in Paris in the years 1882 and 1884。
An important paper of thirty quarto pages published in the
'Transactions of the Royal Society' for June 19; 1862; under the
title 'Experimental Researches on the Transmission of Electric
Signals through submarine cables; Part I。 Laws of Transmission
through various lengths of one cable; by Fleeming Jenkin; Esq。;
communicated by C。 Wheatstone; Esq。; F。R。S。;' contains an account
of a large part of Jenkin's experimental work in the Birkenhead
factory during the years 1859 and 1860。 This paper is called Part
I。 Part II。 alas never appeared; but something that it would have
included we can see from the following ominous statement which I
find near the end of Part I。: 'From this value; the
electrostatical capacity per unit of length and the specific
inductive capacity of the dielectric; could be determined。 These
points will; however; be more fully treated of in the second part
of this paper。' Jenkin had in fact made a determination at
Birkenhead of the specific inductive capacity of gutta…percha; or
of the gutta…percha and Chatterton's compound constituting the
insulation of the cable; on which he experimented。 This was the
very first true measurement of the specific inductive capacity of a
dielectric which had been made after the discovery by Faraday of
the existence of the property; and his primitive measurement of it
for the three substances; glass; shellac; and sulphur; and at the
time when Jenkin made his measurements the existence of specific
inductive capacity was either unknown; or ignored; or denied; by
almost all the scientific authorities of the day。
The original determination of the microfarad; brought out under the
auspices of the British Association Committee on Electrical
Standards; is due to experimental work by Jenkin; described in a
paper; 'Experiments on Capacity;' constituting No。 IV。 of the
appendix to the Report presented by the Committee to the Dundee
Meeting of 1867。 No other determination; so far as I know; of this
important element of electric measurement has hitherto been made;
and it is no small thing to be proud of in respect to Jenkin's fame
as a scientific and practical electrician that the microfarad which
we now all use is his。
The British Association unit of electrical resistance; on which was
founded the first practical approximation to absolute measurement
on the system of Gauss and Weber; was largely due to Jenkin's zeal
as one of the originators; and persevering energy as a working
member; of the first Electrical Standards Committee。 The
experimental work of first making practical standards; founded on
the absolute system; which led to the unit now known as the British
Association ohm; was chiefly performed by Clerk Maxwell and Jenkin。
The realisation of the great practical benefit which has resulted
from the experimental and scientific work of the Committee is
certainly in a large measure due to Jenkin's zeal
快捷操作: 按键盘上方向键 ← 或 → 可快速上下翻页 按键盘上的 Enter 键可回到本书目录页 按键盘上方向键 ↑ 可回到本页顶部!
温馨提示: 温看小说的同时发表评论,说出自己的看法和其它小伙伴们分享也不错哦!发表书评还可以获得积分和经验奖励,认真写原创书评 被采纳为精评可以获得大量金币、积分和经验奖励哦!