Fune 18, I 885 | 
The little -kinematical, or rather quasi-corpuscular, e2- 
cursus to which pp. 71-74 are devoted, is one of the 
richest pieces of Jaradoxing (in De Morgan’s sense) that 
we have ever met with. Here is a little bit of it :— 
** Pouillet, having ascertained the number of thermal units 
imparted to the water in his pyrheliometer of 3°93 ins. diameter, 
imagined that he had measured only the energy of the rays con- 
tained in a pencil of 11°9 square inches section ; whereas, in 
reality, he had, at the end of his experiment of five minutes’ 
duration, subjected his instrument to the action of the entire 
number of rays contained in a passing pencil or sunbeam, 
the section of which we ascertain by multiplying the orbital 
advance of the earth during five minutes, 28,836,000 ft., by the 
diameter of the pyrheliometer, 0°305 ft.” 
Thus it is the zzzber of rays, not the time of exposure 
to one ray, which determines the result ! 
One more quotation, a very short one, must be given. 
It is from p. 136, and we put two words in italics :— 
**Tn view of the fact that projectile force diminishes inversely 
as the square of the depth of the medium penetrated. . . .” 
It is not easy to fix on the exact meaning of this very 
curious statement. Hence we must take it literally, what- 
ever be the consequences. Discussion of penetration 
would obviously be useless in such a case, for the whole 
projectile force (even were it infinite) would be gone before 
penetration had commenced ! 
The immense expense which has been lavished on this 
volume, and on its truly wonderful iliustrations, is calcu- 
lated to produce reflections even more painful than those 
evoked by the perusal of the text itself. From the ma- 
terials here given, something may yet be made, but 
certainly not on the lines chosen by the author. 
We hope, shortly, to return to our store, and to select 
for the instruction and warning of our readers a few 
additional specimens, by no means inferior in quality to 
those just dealt with. G. H. 
PROFESSOR FLEEMING F$ENKIN, LL.D., F.R.S. 
ON Friday last, most unexpectedly and greatly to the 
grief of all his friends, died Prof. Fleeming Jenkin 
at Edinburgh, at the age of fifty-two. He had been in 
somewhat delicate health for a considerable time, but 
was, as usual, personally directing the engineering opera- 
tions in connection with telpherage in London and Sussex, 
and seemed to have greatly gained in health and strength 
when he started for Edinburgh some days before his 
death. But blood-poisoning succeeded a slight surgical 
operation, and his death rapidly followed. 
He was born in Kent in 1833, and was the son of the 
late Capt. Charles Jenkin, R.N. His school-days were 
spent at Jedburgh, Edinburgh, and Frankfort-on-the- 
Maine, while he took his M.A. degree at the University 
of Genoa, and began his engineering career in Marseilles, 
thus acquiring a wide knowledge of languages and of 
peoples which was most valuable to him afterwards in 
his scientific and social life. 
In 1851 he returned to England, and was apprenticed 
to Messrs. Fairbairn’s in Manchester, from which time 
his progress was rapid. We hope that the interest- 
ing and highly creditable history of his subsequent 
introduction as a well-trained mechanical engineer to 
submarine telegraphy (then in its extreme youth) and 
to Sir William Thomson, which led to his soon taking 
charge of the testing of the first Atlantic cable in 1858, 
and to a friendship and partnership with Thomson and 
Varley, will yet be told by some one who can do full 
justice to it. Our grief at Varley’s loss is yet fresh, and 
we deeply sympathise with Sir William Thomson at the 
close of this partnership, the existence of which has been 
synonymous with the progress of submarine telegraphy. 
On the appointment of the Committee of the British 
Association on Electrical Standards Jenkin’s services were 
NATURE 
153 
solicited, and the good work that he did as a member of 
this Committee is amply shown by his large contributions 
to the Reports on Electrical Standards, and which con- 
tain an account of his absolute measurement of the 
capacity of a condenser, the first such determination ever 
made ; and the chapters that he wrote in connection with 
these Reports on the subject of “ Absolute Units” formed 
the only available text-book for the student of mathe- 
matical electricity before about the year 1872. Appended 
to these reports are the Cantor lectures which he de- 
livered on the construction, laying, and testing of sub- 
marine cables, and these lectures showed as wide an 
acquaintance with the practice of electrical science as do 
the other chapters referred to with the theory of the subject. 
In 1865 he was elected a Fellow of the Royal Society 
and Professor of Engineering in University College, 
London, and in 1868 he became Professor in the 
University of Edinburgh, where he created a School of 
Engineering to which considerable numbers of prominent 
Engineers and Professors of Engineering acknowledge 
their indebtedness. In the following year the Royal 
Society of Edinburgh elected him a Fellow, and subse- 
quently he became a Member of the Institution of Civil 
Engineers, having been made an Associate of that Insti- 
tution as early as 1859. In 1883 the honorary degree of 
LL.D. was conferred on him by the University of Glasgow. 
Jenkin’s book on Electricity and Magnetism, published 
in 1873, was a revelation to non-mathematical and even 
to many mathematical men, of the ideas which had until 
then been wrapped up in the mystery of mathematics or 
in the practice of the submarine cable testing-rooms. Sir 
William Thomson had been publishing many detached 
papers on electricity in the mathematical journals, and 
had been applying his knowledge in practice, so that an 
exact science of electrical quantities had been growing up 
among submarine cable engineers ; but the electricity of 
the text-books remained as unscientific and primitive as 
of old: the knowledge of the practical men had become 
indeed far more scientific than the knowledge of the schools. 
Fully recognising this, Prof. Jenkin made in his book a 
totally new departure, and presented electricity and 
magnetism for the first time in a text-book as subjects 
capable of quantitative study. To understand the great 
effect produced by this book, which has now passed 
through many editions, it must be remembered that 
neither Clerk-Maxwell’s treatise, nor Thomson’s reprint 
of his Mathematical Papers appeared until 1873, and that 
at that time “electric potential,” which to-day has its 
commercial unit, was to every one, except the engineers of 
submarine telegraphy, a mere mathematical function. 
In 1882 a lecture was delivered at the Royal Institution 
on Electric Railways, and the system devised by Profs. 
Ayrton and Perry for effecting an absolute block, and 
thus enabling any number of electric trains to be run 
without the employment of drivers, guards, or signalmen, 
was described and exhibited by a working model. An 
account of this was read by Prof. Jenkin, and he at once 
saw that it contained the solution of a plan that he had 
been thinking over for doing on a large scale by electri- 
city what had previously been done on a small scale 
with pneumatic tubes.  TZe/fherage, or the automatic 
electric transport of goods, was the outcome, and the 
development of practical methods of running carriers 
electrically along a steel rod suspended in the air from 
wooden posts, occupied him, with the other two in- 
ventors, during the last three years of his life, the system 
being one which needed new invention in every one of its 
details. His inventive power is described by his assist- 
ants as wonderfully active and prolific, and he had 
energetic characteristics which only seldom accompany 
inventive genius, and which made his cooperation in- 
valuable to the other directors of the Telpherage Com- 
pany. It is deeply to be regretted that, having busied 
himself so actively in the long series of telpherage experi- 
