NATORE 
THURSDAY, JULY 29, 1886 
ELECTRIC TRANSMISSION OF ENERGY 
Electric Transmission of Energy. By Gisbert Kapp, C.E. 
(London: Whittaker and Co., 1886.) 
‘SyAke2 the invention of the electric telegraph the sub- 
ject of the electric transmission of energy is that 
subject which of all others has most attracted the atten- 
tion of practical scientific men. Under this head are 
comprehended every form of telegraph and of telephone, 
electric railways, and the electric transmission of power 
for the driving of lathes and other machines. Even the 
novel apparatus which has been described for enabling 
us to see what is happening at distant places and the very 
transmission of light itself through the interstellar ether 
must be regarded as parts of the great subject which Mr. 
Kapp has undertaken to treat of in this small volume. 
On examining the book, however, it will be found that 
the author has wisely confined his attention to the electric 
transmission of energy for the purpose of its being trans- 
formed at a distant place into mechanical energy for driving 
machinery. Indeed, it may be said that much more than 
half the book is devoted to the subject of the dynamo- 
machine, and that much less than half of it is devoted to 
the subject of the electric transmission of energy. Before 
electric energy can be transmitted it is necessary to 
produce it. It is rather difficult to imagine a store of 
electric energy existing anywhere and ready for trans- 
mission; and hence its production, transmission, and 
transformation into some other form of energy are circum- 
stances which are exactly coincident with one another: 
as its transmission therefore implicitly involves its pro- 
duction and transformation, Mr. Kapp is perfectly justified 
in devoting as much of his book as he pleases to a 
description of the dynamo-machine. 
Few people are better qualified to speak from experi- 
ence of the most recent practice in the manufacture of 
dynamo-machines than the author of this book, and his 
paper entitled “ Modern Continuous-Current Dynamo- 
Electric Machines and their Engines,” read on November 
24, 1885, before the Institution of Civil Engineers, and 
the discussion upon it, are to be regarded as exceedingly 
valuable helps to the electrical engineer. This book will 
be valuable to students who do not possess a copy of Mr. 
Kapp’s original paper. Jt contains additional matter, 
much of it good ; but to some of it we would offer a mild 
objection. For example, some distinction might have 
been made between the magnetic theories of Weber and 
Prof. Hughes. Mr. Kapp has certainly a good working 
knowledge of the theory of the dynamo-machine, and he 
leads up to the theory in a very ingenious way, but we 
are afraid that students will benefit more by reading an 
elementary treatise on electricity and magnetism, the 
writer of which may have had less originality than Mr. 
Kapp, than by taking their elementary notions from this 
book. Thus, for example, the following statement may 
have a perfectly orthodox meaning to Mr. Kapp :—“‘ We 
can either assume that the lines are of different strength, 
and that the mechanical force with which a given free 
magnet pole is urged along any one particular line, is 
dependent on the strength of that line, which may be 
VOL. XXXIV.—No. 874 
285 
different from that of any other line belonging to the 
same field” (p. 18); but it will give great trouble to a 
student who knows that the resultant force is not the 
same at all points in a line of force, and who will find it 
inconsistent with the statements which Mr. Kapp has 
himself to make later on. - 
Again, we are disposed to think that it would be 
graceful in Mr. Kapp, and other makers of dynamo- 
machines at the present time, to give a little more 
credit to Gramme, and to refrain from dwelling so 
much on the great advances which have been made 
in recent years in the construction of dynamo-machines. 
When we compare modern machines with the Gramme 
machine of ten years ago, we see improvements on the 
original machine certainly, but they are very small. They 
consist mainly in ways of winding the conductor on the 
armature, so that it shall not readily slip or heat. How 
little of an essential kind has been introduced in the field- 
magnet arrangement may be gathered from the sheet of 
diagrams given at p. 102 of this book. In fact, a modern 
dynamo-machine may be said to be a Gramme or Sie- 
mens machine, the field-magnet circuit of which has been 
modified in a fanciful manner. Happily such modifica- 
tion in shape, however fanciful, does not seem to have 
impaired very much the efficiency of the arrangement, 
whereas it has enabled makers to greatly alter the outside 
appearances of machines, so that good Gramme and 
Siemens dynamo-machines are no longer called by these 
names, but by the names of the makers who have given 
them such various outside appearances. Large modern 
machines are superior to ancient small machines in 
efficiency and in the “output” per pound weight : firstly, 
because they are larger—and this is the main cause of 
their superiority ; secondly, because the mechanical 
engineers to whom the details in construction have 
always been intrusted are now, some of them, slightly 
acquainted with the laws of electricity and magnetism ; 
and, thirdly, because the manufacture of numerous 
machines has enabled costly manufacturing tools to be 
introduced, and these tools enable a method of construc- 
tion to be employed which would in the past have been 
prohibited by the expense. 
Again, we object somewhat to Mr. Kapp’s use of the 
terms “theoretical” and “ practical.” For example, in 
discussing the efficiency of the electromotor when doing 
various amounts of work, at p. 129, he says that a certain 
statement which he has made is theoretically quite accu- 
rate, but from a practical point of view it requires some 
modification, and he proceeds to show that the want of 
accuracy was due to the fact that all considerations of 
magnetic and material friction had been neglected. We 
should have said in such a case that the statement was 
theoretically quite inaccurate. We consider that much 
mischief is occasionally done by what is usually called the 
comparison of theory and practice. If the mathematical 
results derived from some hypothesis which is evidently 
wrong be called a theory, we must of course have dis- 
agreement between theory and practice, and it is greatly 
in consequence of this that the majority of practical 
engineers have acquired a contempt for theory and for 
the reading of books which deal with the theoretical 
principles underlying their professional work. If the 
results of speculation on absurd hypotheses must be 
oO 
