270 
NATURE 
[4ug. 4, 1870 
schools with 34,283 pupils, the number of teachers at 
present giving instruction in connection with the Depart- 
ment being nearly 1,000. Now, how is this work being 
done? In the first place let us say that it is going 
on among classes of the community which all our 
other educational means do not touch, and, as may be 
imagined, much of the work is night work ; in some cases 
the working men taught have commenced their education 
by building their schoolrooms ; and those who know the 
delights of a laboratory would think that the chemistry was 
acquired by apparatus and appliances which made even 
the simplest experiment an impossibility. 
Secondly, let us say that all the year’s work is brought 
toa focus by examinations held on the same night through- 
out the length and breadth of the land, the papers being 
sent from South Kensington to the local committees with 
infinite precautions, and the answers being returned sealed 
the same night to London. They then are handed over, 
with no indication as to name of candidate or place ot 
examination, to the Government examiners, and when 
we state that these examiners include the names of 
Huxley, Frankland, Ramsay, Tyndall, and others of like 
calibre, we need say no more as to the rigour and fairness 
of the examination. Here is a table showing how this 
ordeal is passed :— 
No. examined.|N® of Papers|No. of Papers 
Year worked. passed. 
1867 4,520 8,213 6,013 
1868 7,092 13,112 8,649 
1869 13,234 24,085 14,550 
It is impossible within the limits of an article to dwell 
upon the various points of inquiry and interest which lie 
around the working of the system: we shall be content if 
we have shown what it is doing, and how the teaching is 
being conducted. When these points are known there 
can be no doubt as to the importance of the work done, 
and, although many improvements may be required, it is 
clear that 77 essentials the Department is now on the right 
track and is doing great good. What is most required is 
systematising and formulating the instruction. Hitherto 
the teaching has been rather desultory. It is very desirable 
that regular systematic courses of instruction, adapted to 
the local requirements, should be imposed as soon as this 
can be done without checking the spread of instruction. 
Some examiners complain of “cram,” but this is not 
limited to the South Kensington system ; and the teachers 
complain of poor pay. This should certainly be corrected; 
the results they are accomplishing are too important to be 
ignored ; and it would seem that the time had almost come 
for a complete inquiry into the whole system in order that 
this important national engine should work with the least 
possible friction and waste of power. 
WHAT [S ENERGY ? 
IV.—THE DISSIPATION OF ENERGY 
ete this point we can imagine some champion of 
perpetual motion coming forward and _ proposing 
conditions of truce. “I acknowledge,” he will say, “that 
perpetual motion, as you have defined it, is quite impos- 
sible, for no machine can creaze energy, but yet I do not 
see from your own stand-point that a machine might not be 
constructed that would produce work for ever. You tell 
me, and I believe you, that heat is a species of molecular 
motion, and hence that the walls of the room in which we 
now sit are full of a kind of invisible energy, all the 
particles being in rapid motion.” Now, may we not sup- 
pose a machine to exist which converts this molecular 
motion into ordinary work, drawing first of all the heat 
from the walls, then from the adjacent air ; cooling down, 
in fact, the surrounding universe, and transforming 
the energy of heat so abstracted into good substantial 
work? There is no doubt work can be converted into 
heat—as, for instance, by the blow of a hammer on an 
anvil—why, therefore, cannot this heat be converted back 
again into work? 
We reply by quoting the laws discovered by Carnot, 
Clausius, Thomson, and Rankine, who have all from 
different points of view been led to the same conclusion, 
which, alas! is fatal to all hopes of perpetual motion. 
We may, they tell us, with the greatest ease convert 
mechanical work into heat, but we cannot by any means 
convert all the energy of heat back again into mechanical 
work. In the steam-engine we do what can be done in 
this way ; but it is a very small proportion of the whole 
energy of the heat that is there converted into work, for 
a large portion is dissipated, and will continue to be 
dissipated, however perfect our engine may become. Let 
the greatest care be taken in the construction and work- 
ing of a steam-engine, yet shall we not succeed in con- 
verting one-fourth of the whole energy of the heat of the 
coals into mechanical effect. 
In fact, the process by which work can be converted 
into heat is not a completely reversible process, and Sir 
W. Thomson has worked out the consequences of this fact 
in his beautiful theory of the dissipation of energy. 
As far as human convenience is concerned, the different 
kinds of energy do not stand on the same footing, for we 
can make great use of a head of water, or of the wind, or of 
mechanical motion of any kind, but we can make no use 
whatever of the energy represented by equally diffused 
heat. If one body is hotter than another, as the boiler 
of a steam-engine is hotter than its condenser, then we 
can make use of this difference of temperature to convert 
some of the heat into work, but if two substances are 
equally hot, even although their particles contain an 
enormous amount of molecular energy, they will not yield 
us a single foot-pound of work. 
Energy is thus of different gvad/ztzes, mechanical energy 
being the best, and universal heat the worst ; in fact, 
this latter description of energy may be likened to the 
dreary waste heap of the universe, in which the effete 
forms of energy are suffered to accumulate, and, alas ! this 
desolate waste heap is always continuing to increase. 
But before attempting to discuss the probable effect of 
this process of deterioration upon the present system of 
things, let us look around us and endeavour to estimate 
the various sources of energy that have been placed at 
our disposal. 
To begin with our own frames, we all of us possess a 
certain amount of energy in our systems, a certain 
capacity for doing work. By an effort of his muscles the 
blacksmith imparts a formidable velocity to the massive 
hammer which he wields: now what is consumed in order 
