50 
projectile is 20 Ibs., and moves with the velocity of 1000 
feet-per second,” before they start on their dynamical 
work they say : the mass or inertia in engineers’ units is 
20 + 32°18, and they use $ mv” and get their answer at 
once—not in foot-poundals or other absurd units—but in 
the foot-pound units in which they think and talk. Such 
students have no troubles and make no mistakes, for 
they use an absolute system in which their answers are 
in the language of their daily life, and not Choctaw. 
Clerk Maxwell said, “In fact, the only occasions in 
common life, in which it is required to estimate weight 
considered as a force, is when we have to determine the 
strength required to lift or carry things, or when we have 
to make a structure strong enough to support their weight.” 
Very well then,in the “common life” of an engineer 
these are the most frequent occasions. He almost never 
needs to speak of the inertia of a body by itself; when 
he needs the idea, it is when on his way to a calculation 
of force or energy. 
so-called absolute units, the C.G.S., and cannot make 
mistakes ; all the other readers of books on dynamics, 
almost all the readers of Maxwell’s “ Heat,” in which the 
above passage occurs, are engineers. And all such 
engineers as do not openly scoff at the teaching of 
science colleges, have had their lives filled with worry 
through the misery of having to use the poundal in 
examinations, and of hearing men who know nothing 
about engineering or engineers, or their lives or their 
needs, declaiming against the want of scientific know- 
ledge shown by the engineer. The evils created by mere 
want of humour in a few influential men have been very 
great. These men speak of the pull of a tram-car in 
pounds, and their students need to use pounds of force 
continually in their laboratories, and they never by any 
chance use the poundal, or need to use it, except in 
working academic written answers to academic questions, 
and in working with an Atwood’s machine. When a 
student speaks of so many pounds of sugar or coals, he 
is not thinking, nor does he need to think, about its 
inertia, and the use of the pound in this connection could 
do no harm, even if g varied ever so much more than it 
does on the surface of the earth. I see no great objec- 
tion to the use of the word wezgAf as meaning the attrac- 
tion of the earth for a body, anywhere. Of course this 
is a variable force, and for practical purposes the weight 
of a pound anywhere on the earth is a force of one pound. 
We are always being told that the pound is legally a 
quantity of stuff, and so it is ; but note the actual wording 
of the Act, ‘ The weight in vacuo of the platinum weight 
declared to be the imperial standard shall be the legal 
standard of weight. . . .”. Now I would ask whether the 
inertia of the standard body is different in vacuo from 
what it is elsewhere. But I refrain from trying to take 
an advantage from the wording of the Act ; and besides, I 
do need for my case the words inserted after vacuo “in 
London,” if the legal weight is to be taken as the force 
of one pound. As the standard piece of metal is kept in 
London, and is not likely to rust or decay, and possibly 
its inertia keeps constant and is not affected by tempera- 
ture, as Prof. Fitzgerald has suggested, perhaps we may 
concede the following as a definition of our absolute unit 
of force : the force of one pound is that which would give 
to a body of 32°18 times the inertia of the standard object 
NO. 1412, VOL. 55 | 
NATURE 
The physicist uses the other set of | 
[ NovEMBER 19, 1896 
kept in London, an acceleration of 1 foot per second per 
second, 
If, however, engineers are to undergo any continuation 
of the persistent scorn of the last thirty years, let our 
scorners show some scientific knowledge of our position, 
and let us hear no more of the engineers’ unit of force 
being the force of gravity anywhere or everywhere upon 
the standard weight. 
As for our useful term centrifugal force, even our 
worst opponents are beginning to find out that there was. 
a third of Newton’s laws of motion, and that we may 
ask: If a body is acted upon by centripetal force, there 
is an equal and opposite force acting ; and if it is not the 
body that exerts this force, what is it? If the body 
exerts this force, surely we have a right to call it the 
centrifugal force of the body. 
I would, therefore, make an appeal to our academic 
enemies : Your students are nearly all young engineers 
of one kind or another. Why not be satisfied with 
teaching them about absolute units only—the C.G.S. 
and the foot, second, force of one pound, system ? 
You now use three others: the so-called British or 
poundal system, the gramme gravitational and the pound 
gravitational systems. It is only, after all, an error of 
judgment, like the crime of Surajah Dowlah or the St. 
Bartholomew, and you probably do not know what a 
complicated mess you make of a young engineer’s mind ;. 
and we are quite willing to imagine that it is only ignor- 
ance and prejudice, and not antagonism to education 
that impels you to retain this want of system. But one 
effect is this. Your finished engineering students can- 
not get into works without paying high premiums ; such 
is the prejudice of the experienced engineer against 
college-bred men, a prejudice which I myself would 
again have if I were again to act as a manager of 
works. 
Every now and again an academic friend will say such 
things as these, “ Well, if he cannot take in these ideas,, 
he is not fitted to be an engineer.” “If he has all that 
difficulty about Euclid, he is not fitted to be an engineer.” 
And these academic statements are made about young 
men who are heaven-born engineers, fellows who never 
tire of fiddling with engineering things, and who are sure 
to succeed in actual engineering work, and who, when 
they do succeed, will scorn the idea that there is any 
use in a scientific education, and “what for no?” Iam 
very thankful that entrance to all professions is not by 
examination. Our friends, worshipping the German 
soul-destroying educational fetish, insist on the very 
worst system of education for the average Englishman ; 
and when a healthy young soul refuses to be destroyed, - 
you punish its owner by shutting him out of the very 
professions for which he is best fitted by your wretched 
examinations. You say he cannot think, and you actually 
make him believe it too, because he refuses your 
Duchaylus’ proofs and the metaphysics of Alexandrian 
philosophers. He ought, I suppose, to be grateful that 
you do not insist on his spending a year in learning the 
Trireme method of multiplication, or what right he has. 
to say that one line is twice the length of another. Alice’s 
White Knight was not more protected from imaginary 
dangers than the young men who now are being prepared 
for their life’s work by a wasteful and pedantic trifling 
