Vol. XXIV. No. i.] 
POPULAR SCIENCE NEWS. 
5 
Practical Cljcnjistry aijd tlje ^rts. 
THE ENGLISH CHANNEL BRIDGE. 
The accompanying engraving (from I^a 
Nature) represents a view of the proposed 
bridge across the English Channel, as it will 
appear after completion. This project is cer- 
tainly a bold and magnificent conception, 
and, if ever carried out, the bridge will be 
the greatest feat of engineering ever accom- 
plished. The preliminary plans have been 
made for the work, but, before it becomes an 
accomplished fact, many obstacles — not only 
natural ones, but financial and political — 
must be overcome. 
The proposed bridge will start from near 
Folkestone, in England, and cross to a point 
near the port of Ambleteuse, on the French 
coast. The total length will be about twenty- 
iour miles, but it will deviate from a direct 
line, in order to cross two banks, or shoals, 
in the middle of the channel, and obtain the 
advantage of the 
shallow water (20 
to 30 feet) above 
them. In the deep- 
est part of the chan- 
nel the piers must 
be sunk in 165 feet 
of water — a feat 
which will require 
some skillful en- 
gineering. 
The piers, of 
which there will 
be about 125, will 
be of solid masonrj-, 
and will be built 
near the shore in 
caissons, and then 
floated out into the 
channel and sunk 
in their proper 
places. They will project 60 feet above 
low water, and on them will rest the 
steel cylindrical columns, 120 feet in height,^ 
which support the superstructure of the I 
bridge, making a clear height of 180 feet 
above the water, and allowing ample room 
for vessels with the highest masts to pass 
freely beneath. The construction and placing 
of each pier is estimated to take about a year, 
although, of course, an indefinite number can. 
be constructed at the same time. i 
The length of the spans will vary, but the 
widest will consist alternately of 900 and | 
1,500 feet, each span of the bridge (as shown I 
in the engraving) resting upon two piers. 
The narrowest span will be 300 feet. Over 1 
a million tons of metal will be used in the 
work, and the cost is estimated at from 175 
to 200 millions of dollars. About ten years 
will be required to complete it, and, if the , 
success is assured, it would seem to be an j 
easy matter to raise the necessary funds. I 
The commercial and political importance 
of this bridge, which would give Great 
Britain direct and unbroken railroad commu- 
nication with all parts of the eastern hemis- 
phere, can hardly be overestimated, and it 
would also tend to bind the European nations 
more closely together and prevent war. Mr. 
Gladstone is reported to have said that "by 
either the tunnel or the bridge the peace of 
the world is assured," and, although this may 
be rather a sanguine view to take of the mat- 
ter, there can be no doubt that the result of 
such direct means of communication would 
be an unqualified blessing to all concerned, 
and it is to be hoped that the ridiculous fears 
of foreign invasion which led the British 
government to suppress the already com- 
menced tunnel underneath the channel, will 
not be the cause of the abandonment of the 
proposed bridge above its tempestuous waters. 
stopping, starting, or reversing the motion, 
and safety catches, to prevent its fall in case of 
the breaking of the chain, can be readily 
attached to it. No attendant is required, as 
its operation is so simple that anyone can 
make use of it without danger, and means 
can easily be arranged by which it can be 
brought back to the foot of the staircase by a 
person standing below, if it has been left at 
the top by the last passenger. 
This invention is nuich less costly than a 
regular elevator, and seems to be especially 
applicable to private houses, stores, small 
hotels, and similar buildings. It will doubt- 
less come into quite extensive use. 
A NOVEL ELEVATOR. 
The ingenious device for ascending stair- 
cases shown in the illustration (on page 6) 
was exhibited at the Paris Exposition last 
summer by M. Amiot, under the name of 
monte-escalier. It is intended as a substitute 
for the more expensive elevator in private 
houses, and buildings where the travel from 
one story to another is small, besides being 
adapted to narrow and crooked locations, 
where the regular type of elevator could not 
be introduced, for want of sufficient space. 
The engraving leaves little to be explained 
in regard to its construction and working. 
The whole installation may be divided into 
three parts : the rails, which are attached 
firmly to the side of the staircase, which may 
be either straight or curved ; the car, which 
is a platform resting on the rails by wheels ; 
and the motor, which may be either hydraulic, 
electric, or of any other type, according to 
circumstances, and which draws the car from 
one story to the other by means of a chain. 
The car is provided with a simple means •f 
TRANSPARENCIES IN PRUSSIAN BLUE. 
Mr. Robert Benecke, of St. Louis, gives instruc- 
tions in Anthony's Photographic Bulletin, to select 
glass free from scratclies and bubbles, put it in a 
solution of washing soda for a time, wash, and f.»t 
it up to dry. Now take one ounce of fine gelatin., 
such as is used for making dry plates, put it in clean 
water; wash it a couple of times, squeeze out the 
water and place it on 
a clean towel. After 
about one hour, dis- 
solve the gelatine in 
twenty ounces of hot 
water, and filter it 
through cotton, flan- 
nel, silk, or buckskin 
pushed into the neck 
of a funnel. Coat the 
plates with the gela- 
tine solution wanned 
from 120° to 140° 
Fahr. In cold weather 
it will be necessarv to 
warm the plates. When 
the solution is spread 
evenly over the glass, 
lay it on a cold marble 
slab placed horizon- 
tally, and as soon as 
the coating has be- 
come stiflf enough not 
to run, set the plates 
up on nails to dry. This will take from eight to 
twelve hours or more. Any number of plates can 
be thus prepared, and may be kept for any length of 
time in a place free from dust. Next mix the sensi- 
tizing solution. Dissolve citrate of iron and ammo- 
nia, 71/2 drachms in 4 ounces of water, also ferricya- 
nide of potassium, 5 drachms in 4 ounces of water. 
Mix and filter into a dish, and immerse the plates 
about five minutes, avoiding air bubbles. This is 
better done in the evening by lamp-light. Next 
morning they will be dry, and ready to be placed 
under the negative and exposed. The time for 
printing required is about double that for albumen- 
ized paper. The last thing to be done is the wash- 
ing, which removes the salts and develops a rich 
blue print. The solution must be freshly made, as 
it will not keep very long after being used. The 
plates will keep in the dark for some time. 
There was at the Paris Exhibition a coal-digger 
which is worked by an electro-motor. By its aid a 
man and helper can uncfercut one hundred and ten 
tons of coal in ten hours, in a seam six feet 
thick, and the power required for this at the 
pit-head it a little over two and one-quarter horse- 
power. 
