The Sun.
London, England, 1866-07-04 00:00:00

Progress of Science in America.

(From the New York Daily Tribune, June 9.)
MODERN IMPROVEMENTS IN TELEGRAPH APPARATUS-
TUNNELLING-CANONS.

At A recent meeting of the Polytechnic branch of the
American Institute, Professor Tilman, the chairman, read
a paper on " the Galvanometer," showing that it is possi-
ble to arrive at the actual intensity or force of any gal-
vanic current fpy the application of Amphere's formulas to
the motion of the sensitive needle ; but as a long calcula-
tion would have to be made for each case separately, and
as the elements entering into the calculation were liable
to change, it was important to find a ready means of gra-
duating the scale of deflection. Several distinguished
philosophers had used the galvanometer in connection with
the Thermo-pile for the purpose of determining minute
differences in temperature. Nobili and Becquerel had en-
deavoured to fix the scale by the use of pairs of rods
heated at alternate joints. Melloni had also used a simi-
lar method. Poggendorff proposed to reach the same re-
sult by using coils at various inclinations to the magnetic
meridian. Dr. L. Bradley, of our own country, who was
present with apparatus, had recently brought out means
whereby the use of the galvanometer would be greatly
improved, and become of real service in delicate and exact
measurement of electrical force.
Dr. Bradley exhibited his apparatus for measuring the
amount of resistance offered by different telegraph instru-
ments to the passage of the current. The common gal-
vanometer attached to the Rheostat shows by the deflec-
tion of the magnetic needle the effect of the resistance,
and the amount of the deflection is somehow related to the
amount of resistance, but exactly how has never yet been
ascertained. The world wants a good measure for com-
paring one resistance with another. The resistance offered
by every mile of distance over which an electric signal
travels is considered as a unit.

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He has taken as his unit that adopted by our country-
men. General Lefferts, and Moses B. Farmer, who had
succeeded in producing a very compact and convenient
form of Rheostat, using spools of fino wire, the passage
of the current through which was equal to any desired
length of line. Tho doctor had arranged a series of
these, adjusted with great taro in a single compact in-
strument, provided with a delicate slide, lover, switches,
&c., whereby a greater or less number could be turned
on, so as to attain any desired amount of resistance,
and show exactly what is the length of line equal to that
resistance.

Some instruments forrecciving and recording the signals
used in telegraphing produce a resistance equal to 10 or 21)
miles of line, while others are so constructed or adjusted
as to induce a resistance equal to 100 miles or more. The
instruments with groat resistance work with a weaker
current, and all are adapted for certain situations.
The instruments having coils of slight resistance should
be arranged along the middle of the line, and those of
great resistance at the ends. This apparatus would mea-
sure and assort them with great facility.
A great simplification of battery, lately invented by Dr.
E. A. Hill, of Chicago, was also exhibited. This dispenses
with the porous cup heretofore considered necessary be-
tween the two solutions. It had been found that the differ-
once in the specific gravities was sufficient to keep them
separate with proper care: Instead of arranging the zinc
plate around the copper plate with the porous partition
between, as in the popular Grove battery, Dr. Hill uses flat
plates located one above the other with no partition be-
tween. The copper plate lies near the bottom of the cup,
the zinc plate near the top. The cup is nearly filled with
sulphate of zinc and allowed to become quiet. The sul-
phate of copper is then gently introduced in the form of solid
crystal, which falls to the bottom of the cup, and there soon
dissolves. The result, the familiar blue solution, lies in a
tolerably distinct stratum at the bottom. Caro must be
taken not to introduce so much of the copper sulphate as to
mingle quite up to the zinc plate, as in such case .local
action will result, and the copper will be deposited on the
zinc, causing considerable mischief. To prevent the
chance of this the plates are placed a considerable dis-
tance apart, which increases the resistance of the battery.
The speaker had tested this in his own practice as a
manufacturer and fitter-up of such apparatus, and com-
mended it highly. He had found this battery less efficient,
cup for cup, than the Grove, but the result was a greater
economy. He estimated 100 of these cups equal to 40 of
the Grove, but the cost of maintenance of the whole was
only about ono-fifth. The consumption of materials was
only one-half as great as by the very economical battery
known as Chester's, or the Chronic Acid battery.
Smee's battery was very efficient in depositing metals
for electro-motallurgical, purposes, but was too irregular
and too fiery to bo recommended for telegraphing. It was
of very little use for that.
In practice telegraphing was very much affected by the
state of the weather. In good weather 100 cups of the
Hill battery above described operated eight lines—meaning
eight wires--in the United States Company's office, while
in bad weather it will work but two properly.
Mr. Stetson, the Secretary, said that imperfect insulation
affected the efficiency of telegraphic communications very
materially. Even webs produced by insects in some
otherwise goods forms of insulators militated strongly
against their success in wet weather, particularly in gales of
wind. Every spider's web extending between the wires and
theneighbouring conducting surfaces serves as an efficient
conductor to lead away the current. There is a loss at
every telegraph pole.

Dr. Bradley said that Do La Rivo had suggested that the
tangent of the angle of deflection of the magnetic needle,
exposed to the current in tho galvanometer, might be con-
sidered as approximating to the true measure of resistance.
The Doctor believed that this was an absolutely exact
measure, but has not yet proved it to his satisfaction
by actual experiment. These forces acted against each
ether precisely as opposing weights fixed on a wheel at
the two extremities of a quadrant.
Dr. Rowell exhibited a very perfect:cut-off or balance
valve for use in steam-engines. The introduction of a cut-
off valve in the steampipe at any considerable distance from
the :engine had been found to produce no good effect. If
placed very close, directly on the main valve, it was useful.
Very great progress had been made in this direction, as
also for facilitating the movements of large slide valves,
within the last few years.
Mr, Hyde exhibited an ingenious hammer, operated by a
crank, to bo used for striking drills in an inclined or hori-
zontal position in drilling rock. It was particularly useful
in tunnels where drills were introduced inclining upward.
The machine woßld operate a hammer weighing 25 pounds
with ease. Men can strike directly with sledges either
perpendicular down, or slightly inclined, but this instru-
ment greatly reduces tho labour in striking upward. There
is eccentric gearing which draws the hammer backward
slowly, but strikes it quickly forward.
The well-known Geologist, Dr. Stevens, invited atten-
tion to the peculiarities of the mammoth gullies, or canons
produced by the rivers west of the Rocky Mountains. Our
neighbour the Niagira had excavated a gully 350 feet
deep. The Ohio, near Wellsville, had similarly washed
the earth away to a depth of 700 feet below its original
formation. But the Black Canon whore the Colorado
passes through the Black Mountains, runs for a consider-
able distance
.through an elevated plateau, the general
elevation of which is a mile above its surface. At
one point there is absolutely a perpendicular precipice as-
certained by a careful barometric measurement to be ono
mile in height. At ono point the surface is 6,000 feetabove
the river. His remarks on this, as also on the peculiar
Steppes or offsets in the formation. of the State of New
York measured on the meridian, from the Cattskills across
the valley of the Mohawk to tho Adirondack, wero illus-
trated by large diagrams.