78 
MAGAZINE OF SCIENCE AND ART. 
materials to that on the outside, for a depth of four feet, 
in which I am in hopes the heavier particles of solid matter 
held in mechanical suspension by the water will be re¬ 
tained ; so that after this double process of upward and 
downward filtration, the water will enter the pipe in a 
state comparatively pure and fit for use, The dam wall is 
now rapidly approaching completion, and I think I may 
say that when finished it will, as a specimen of masonry, 
bear comparison with anything else of its kind in the 
colony. 
The contractor for the work has been Mr. Randle, of 
whom I consider it only justice to say, that l have always 
found him most anxious to carry out his work In a manner 
creditable to himself and satisfactory to me. 
At some future time I propose to do myself the honour 
of hying before the society a drawing of the travelling 
derrick, by which the heaviest stones used in the construc¬ 
tion of the wall, weighing sometimes as mnch as five tops 
and upwards, can be moved about by four men and set in 
their places with as much case and accuracy as a bricklayer 
could place a brick. Without such facilities it would have 
been impossible to set stones of the magnitude of those 
used in the work with the requisito degree of precision. 
The only thing now remaining to be done, to supply the 
inhabitants of Parramatta whh an abundance of good 
water, is to lay down the piping for its distribution, and 
this it is to be hoped will not be long delayed. 
The paper was listened to with attention, and loudly 
applauded at the close. 
Some conversation on the subject treated upon then took 
place, after which the proceedings terminated. 
At the meeting of the Philosophical So- 
ciety, held August 12, 1S57, the following 
Paper was read by the Secretary, after the 
Paper on Railways by His Excellency the 
Governor-General:— 
REMARKS ON COLONIAL RAILWAYS. 
WITH REFERENCE CHIEFLY TO MOTIVE POWER. 
In deciding upon the principles according to which a 
great national work, such as a system of railways, 
should bo laid out in a country like Australia, many 
circumstances and facts must bo taken into considera¬ 
tion. . . 
It would be an endless task to point out the interests 
and relations which would be more or less affected by 
the introduction of this inode of traffic on an extensive 
scale, and it may be well to look to the proceedings of 
other countries in reference to this important subject, 
so that vo may avoid their errors. 
The present’social aspect and condition of the Aus¬ 
tralian colonies differ considerably from those of Euro¬ 
pean conntries, and it is well known that they present 
a surface very different from that of other countries ; 
and that the population is by no means a dense one ; 
and tliat this sparse population isinN ew South w ales 
scattered over an extent of country more than 900 miles 
in length, from North to South, by about 300 miles in 
width from East to West. Various circumstances have 
since the first occupation of the colony led to the wide 
dispersion of the inhabitants, while m their natural 
state the lands, though far from being rich, offer veri- 
extensive pasturage, and afford the easy means of rear¬ 
in'. sheep and cattle in large numbers, but as every 
step in the Western interior leads the shipowner fur¬ 
ther from the sea, the limit in this direction appears to 
be already attained on the borders of the great cential 
When the great expense of constructing railways is 
taken into consideration, formed after the model of 
British and European linos, it appears obvious that m 
the present circumstances of the colony, such costly 
works as high speed railways must bo superseded bv a 
more economical method ; for it is a well known tact 
that the cost at which goods and passengers can be car¬ 
ried on a railway, so as to afford a remunerative return, 
will be as the interest on the capital expended, pills tho 
cost of working the line, and inversely, as tho number 
of passengers, or quantity of goods carried. 
It is clear that the profits of a railway are determined 
by the ratio of the proceeds to the cost. The public, 
therefore, is interested as much in the economy of rail¬ 
ways as in tho economy of manufactures; and if the 
pul'd ic is to be benefited by economy being exercised 
in the construction of a railway, causing a reduction in 
the rate of convevance per mile, this shews how essea- 
tial it is to the success of any railway system on a large 
scale in Australia, that the coat of construction should 
bo kept as low as possible. 
The principles of Tailway economy arc better under¬ 
stood now than they were some few years ago. Had 
they been equally well known and acted on at that 
time, an immense saving might have been effected in 
the cost of construction of British railways, os well as 
of the first Australian railway to Parramatta, a work 
which has involved an outlay of nearly £61)0,000, or 
about £10,000 per mile, which is the average cost of 
British railways, the average net returns of which do 
not exceed 3 per cent, on the amount of capital ex¬ 
pended. Such is the result of the vast outlay upon 
railways in Great Britain. For instance, calling tho 
gross revenue of a road paying 10 per cent £1,000, and 
calling the cost of working the line 50 per cent, or 
£500 ; then £500 will be left, which will he equal to 
10 per cent, on a capital of £5,000. 
But if we double the capital, and make it £10,000, 
then £500 will onlv yield a net return of 5 per cent. 
Double the capital again to £20,000, and the return is 
reduced to 21 per cent. 
The capital ought not to be doubled, thcretore, unless 
one of two things is to he accomplished—cither that the 
cost of working the line he greatly reduced, or that the 
gross proceeds he doubled. In order to increase tho 
latter, the rates of conveyance have been raised ; but 
this method is seldom effective, as an increase of 
charges beyond a certain limit has been generally found 
to diminish the proceeds, and to drive tho travelling 
public off the rail, and hack to the load. It it should 
by chance prove effective, the public will suffer by- 
having to pay the higher rates ; and the fair inference 
to be drawn from these facts is, that such works as rail- 
wavs should he promoted so as to produce good me¬ 
chanical results, at tho least possible cost, and that the 
probable traffic be sufficient to justify this cost. 
Before auv general system of railway communication 
can be adopted and acted upon in Australia, the great 
question of the motive power to bo used must first be 
decided. And, in order to enable us to decide whether 
the mode of working a line by horsepower or by loco¬ 
motive engines is tho most suitable and. advantageous, 
under tho peculiar circumstances, attending the intro¬ 
duction of railways in Australia, it is necessary to re¬ 
vert to some of tlie first principles connected with the 
laws of motion, and of retardation. These fimt prin¬ 
ciples will enable us to trace the points of difference 
between the two methods, and will afford the best 
means of arriving at a just and rational conclusion on a 
subject of considerable importance, both in an engineer¬ 
ing and an economical point ot view. 
According to the first principles of mechanics, we are 
told that the same power which conveys a load at the 
rate often miles an hour will convey double that weight 
at five miles an hour, in the same time; or the general 
law is, that the product of a weight, and the velocity 
with which it is mover!, being the same for two different 
velocities, the same power will be required in both 
cases. This is only expressing, in other words, the 
general law, that the velocities will be in the inverse 
ratio of the weights, the power being the same. 
Mechanicians define this principle by paying that 
what is gained in power is lost in time. . And this 
simple proposition, abating fiction, is of universal ap¬ 
plication to all machines, however complicated they 
may be. 
