476 


“colleges” in which it is professedly taught as a system ; and 
yet there seems to be no method applied to the inculcation of 
natural science more misunderstood than this, and no teaching 
in our schools, at present, more utterly destitute of good results. 
Ninety-nine out of a hundred who talk so glibly of object teach- 
ing forget that it is merely a method—a method that has for its 
end to inculcate knowledge ; that this knowledge to be incul- 
cated is the essential part of the lesson ; and that a shorough 
acquaintance with the subject must precede any application of this 
mere method of instruction. ‘To stand up and give a lesson upon 
acat, without knowing the first principles of natural history, is 
simply to go through a farcical parody ; and authorities who have 
no better conception of the purposes of object teaching than 
this, set the cart before the horse ; or, rather they never hitch 
on their should-be-useful animal at all, but ride off upon this 
hobby, leaving the load of knowledge it was meant to draw stand- 
ing in the ruts—where it has been standing, as Prof. Huxley 
admirably puts it, ever since the days of ancient Rome. 
‘¢Tt has been recently advocated that every public school should 
be supplied with a collection of objects to illustrate the funda- 
mental facts of natural science. By all means let it be so; but 
let the first use to which these are put be to instruct the teachers 
themselves in what they will have to teach. Let them learn 
what there is in each object of educational value, and what are 
its worthless characters ; let them recognise that no object is 
complete in itself, but is merely a part of a vast whole, and that 
their office is to lead the child to recognise its most important 
relations to other objects. In building up the edifice of know- 
ledge, they must not use every rough stone indiscriminately, but 
they must teach the little builders to chip off the useless angles 
of selected pieces, and so shape them that every stone shall, at 
its proper time, fit into its proper place. If this be not done, 
the most instructive objects in the world will not raise its single 
line of substantial structure, but will rest upon the minds of the 
pupils as an unarranged heap of meaningless facts—facts which 
will not even be long remembered ; and it is as well that they 
should not be, because utterly useless, being unconsolidated by 
any cement of reason. 
‘* We fear that no better end is attained by, or can be hoped 
for from, object-teaching in our public schools, until, as we have 
said, the teachers themselves are thoroughly educated in the 
principles of natural science. To accomplish this, however, 
the ear of these who rule the teachers must be gained ; and we 
raise the question whether the representatives of science should 
not have a voice inthe management of our public school system ? 
As object-teaching is a mere handmaid of science, is of use only 
to givescientific habits of thought, and to convey a knowledge 
of svientific facts, and is worthless without science, the public 
should see that its introduction into our schools Le carried on 
under the advice of scientific experts, who shall direct what is 
best to be taught, and advise with the adepts in teaching how 
such knowledge may best be imparted. As a journal having 
the interests of science and education at heart, desiring to see 
science soundly popularised, and the masses made acquainted 
with its technical value, we make this suggestion, and further- 
more ask: Is there any man of scientific attainments in the 
present Board of Education? Is there any scientific authortiy 
upon its general staff? And how many teachers favourably 
known to and having the confidence of the really scientific portion 
of the community are engaged in giving scientific instruction in 
our public sehools ?” 

TRANSMISSION THROUGH PNEUMATIC 
TUBES* 
HE writer having been employed in designing the extension 
of a pneumatic despatch line in which some heavy gradi- 
ents were unavoidable, and it became necessary to ascertain 
by calculation the steepest gradient that could be employed 
so as to obtaina sufficient carrying capacity in the new section 
of the line under given conditions of engine power and of 
length. Almost every text-book and paper on the velocity of 
gases in pipes gave a different formula, and the author therefore 
found it necessary to attempt to construct a convenient ex- 
pression for the speeds of carriers of given weight and fiction, 
under various conditions of pressure, gradients, and dimensions 
of tube. The problem of a successful pneumatic system 
* Abstract of a paper read at the Liverpool Meeting of the British 
Association. 
NATURE 



{| April 13, 1871 

is simply this: To make a given quantity of air expand from 
one pressure to another in such a way as return a fair equivalent 
of the work expended in compressing it. It is obviously im- 
possible to regain the full equivalent of the work, because the 
compression is attended with the liberation of heat, which is 
dissipated and practically lost. Therefore, in designing a pneu- 
matic system, the first thing is to contrive means of compressing 
the air as economically as possible ; and, in the second place, to 
get back the available mechanical effect stored up in the com- 
pressed air, irrespectively of the work employed in compressing 
and examining it. The writer considers that small pneu- 
matic tubes may be worked more profitably than large ones. 
The great convenience of and practical facilities for working 
small letter-carrying tubes”have been amply proved by the 
extensive systems already laid down in Paris, Berlin, London, 
and in other towns, as adjuncts to the telegraphservices. Tubes 
of somewhat larger diameter would undoubtedly work satis- 
factorily. Even still larger tubes, if of moderate lengths, 
might also be found useful for a variety of special appli- 
cations. But the author does not believe that a pneumatic 
line working through a long tunnel could, for passenger traffic, 
ever compete in point of economy with locomotive railways. 
A pneumatic railway is essentially a rope-railway. Its rope is 
elastic, it is true, but it is not light. Every yard run of it, ina 
tunnel large enough to carry passengers, would weigh more than 
;cwt. And it is a rope, too, which has to be moved against 
considerable friction, and in being compressed and moved wastes 
power by its liberation of heat. Ina pneumatic tunnel, such as 
that proposed between England and France, in order to move a 
goods train of 250 tons through at the rate of twenty-five miles 
an hour, it would be necessary to employ simultaneously a pres- 
sure of I4lb. per square inch at one end, and a vacuum of 
13lb, per square inch at the other. The mechanical effect 
obtained with these combined—pressure and vacuum—would be 
consumed as follows :— 
In accelerating the air . . 29 
In accelerating the train. 12 
By friction of the air . 5721 
By friction of the train 330 
The resistance of the air, therefore, upon the walls of the 
tunnel would alone amount to 93 per cent. of the total mechani- 
cal effect employable for the transmission; while the really 
useful work would be only about 54 per cent. of it. And to 
compress and exhaust the air to supply these items of expendi- 
ture of mechanical effect, engines would have to exert over 
2,000 horse power at each end during the transmission, even on 
the supposition that the blowing machinery returned an equiva- 
lent of mechanical effect suchas has never yet been obtained. 
This would not be an economical way of burning coals. 
ROBERT SABINE 
millions of 
foot pounds. 


SCIENTIFIC SERIALS 
Silliman’s Journal, January, 1871. The opening article in 
this number’ is by Prof. J. D. Dana, **On the Quaternary or 
Post-tertiary of the New Haven Region,” in which he proves 
from numerous observations that the glacial era in this district 
was an era of glaciers and not of icebergs, many evidences of 
glacier action being visible in the form of broad furrows from 
eight to ten inches in depth, and extending for long distances on 
beds of trap and granite. —The second paper is by Prof. W. A. 
Norton, ‘*On the Corona seen in Total Eclipses of the Sun.” 
The author attributes this phenomena to a solar aurora, but the 
observations on the recent eclipse will probably induce him to 
modify his opinions ; his arguments being based on the observa- 
tions made during previous eclipses, when the corona was not 
made such a special object of investigation. He lays great stress 
on the long streamers as indications of auroral action, though it 
now appears that these streamers are not so decidedly of solar 
origin as was supposed.—In a letter to Dr, W. Gibbs, Mr. O, 
N. Rood gives a short account of some experiments to determine 
the duration of lightning flashes. A cardboard disc, with fifteen 
narrow and radial apertures, was caused to rotate very rapidly on 
a pin. Occasionally, during a flash, the slits in the cardboard 
were seen distinctly as if the disc were stationary, but more 
usually they were distinctly elongated. From the observations 
made it would seem that the duration of the flashes was about 
iz of a second. The accuracy of this result may perhaps be 

rendered doubtful from the fact that both Becquerel and Faraday 
have noticed that gases are rendered slightly phosphorescent by 
