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[Illustration]




SCIENTIFIC AMERICAN SUPPLEMENT NO. 822




NEW YORK, October 3, 1891

Scientific American Supplement. Vol. XXXII, No. 822.

Scientific American established 1845

Scientific American Supplement, $5 a year.

Scientific American and Supplement, $7 a year.

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TABLE OF CONTENTS.


I.    ANTHROPOLOGY.--The Study of Mankind.--A review of Prof.
      Max Muller's recent address before the British Association.  13141

II.   CHEMISTRY.--Standards and Methods for the Polarimetric
      Estimation of Sugars.--A U.S. internal revenue report on
      the titular subject.--2 illustrations.                       13138

      The Formation of Starch in Leaves.--An interesting
      examination into the physiological _role_ of leaves.--1
      illustration.                                                13138

      The Water Molecule.--By A. GANSWINDT.--A very interesting
      contribution to structural chemistry.                        13137

III.  CIVIL ENGINEERING.--Demolition of Rocks under Water
      without Explosives.--Lobnitz System.--By EDWARD S.
      CRAWLEY.--A method of removing rocks by combined
      dredging and ramming as applied on the Suez Canal.--3
      illustrations.                                               13128

IV.   ELECTRICITY.--Electrical Standards.--The English Board of
      Trade commission's standards of electrical measurements.     13129

      The London-Paris Telephone.--By W.H. PREECE,
      F.R.S.--Details of the telephone between London and
      Paris and its remarkable success.--6 illustrations.          13131

      The Manufacture of Phosphorus by Electricity.--A new
      industry based on dynamic electricity.--Full details.        13132

      The Two or Three Phase Alternating Current Systems.--By
      CARL HERING.--A new industrial development in electricity
      fully described and graphically developed.--15
      illustrations.                                               13130

V.    GEOGRAPHY AND EXPLORATION.--The Grand Falls of
      Labrador.--The Bowdoin College exploring expedition and
      its adventures and discoveries in Labrador.                  13140

VI.   MECHANICAL ENGINEERING.--Improved Changeable Speed
      Gearing.--An ingenious method of obtaining different speeds
      at will from a single driving shaft.--2 illustrations.       13129

      Progress in Engineering.--Notes on the progress of the last
      decade.                                                      13129

VII.  MEDICINE AND HYGIENE.--Eyesight.--Its Care during Infancy
      and Youth.--By L. WEBSTER FOX, M.D.--A very timely
      article on the preservation of sight and its deterioration
      among civilized people.                                      13135

      The Use of Compressed Air in Conjunction with Medicinal
      Solutions in the Treatment of Nervous and Mental
      Affections.--By J. LEONARD CORNING.--The enhancement of
      the effects of remedies by subsequent application of
      compressed air.                                              13134

VIII. MINERALOGY.--A Gem-Bearing Granite Vein in Western
      Connecticut.--By L.P. GRATACAP.--A most interesting
      mineral fissure yielding mica and gems recently opened.      13141

IX.   NATURAL HISTORY.--Ants.--By RUTH WARD KAHN.--An
      interesting presentation of the economy of ants.             13140

X.    NAVAL ENGINEERING.--Armor Plating on Battleships--France
      and Great Britain.--A comparison of the protective systems
      of the French and English navies.--5 illustrations.          13127

      The Redoutable.--An important member of the French
      Mediterranean fleet described and illustrated.--1
      illustration.                                                13127

XI.   TECHNOLOGY.--New Bleaching Apparatus.--A newly invented
      apparatus for bleaching pulp.--2 illustrations.              13133

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THE REDOUTABLE.


The central battery and barbette ship Redoutable, illustrated this
week, forms part of the French Mediterranean squadron, and although
launched as early as 1876 is still one of its most powerful ships.
Below are some of the principal dimensions and particulars of this
ironclad:

    Length           318 ft. 2 in.
    Beam              64 "   8 "
    Draught           25 "   6 "
    Displacement    9200 tons.
    Crew             706 officers and men.

[Illustration: THE FRENCH CENTRAL BATTERY IRONCLAD REDOUTABLE.]

The Redoutable is built partly of iron and partly of steel and is
similar in many respects to the ironclads Devastation and Courbet of
the same fleet, although rather smaller. She is completely belted with
14 in. armor, with a 15 in. backing, and has the central battery
armored with plates of 91/2 in. in thickness.

The engines are two in number, horizontal, and of the compound two
cylinder type, developing a horse power of 6,071, which on the trial
trip gave a speed of 14.66 knots per hour. Five hundred and ten tons
of coal are carried in the bunkers, which at a speed of 10 knots
should enable the ship to make a voyage of 2,800 knots. Torpedo
defense netting is fitted, and there are three masts with military
tops carrying Hotchkiss revolver machine guns.

The offensive power of the ship consists of seven breechloading rifled
guns of 27 centimeters (10.63 in.), and weighing 24 tons each, six
breechloading rifled guns of 14 centimeters (5.51 in.), and
quick-firing and machine guns of the Hotchkiss systems. There are in
addition four torpedo discharge tubes, two on each side of the ship.
The positions of the guns are as follows: Four of 27 centimeters in
the central battery, two on each broadside; three 27 centimeter guns
on the upper deck in barbettes, one on each side amidships, and one
aft. The 14 centimeter guns are in various positions on the
broadsides, and the machine guns are fitted on deck, on the bridges,
and in the military tops, four of them also being mounted on what is
rather a novelty in naval construction, a gallery running round the
outside of the funnel, which was fitted when the ship was under
repairs some months ago.

There are three electric light projectors, one forward on the upper
deck, one on the bridge just forward of the funnel, and one in the
mizzen top.--_Engineering._

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ARMOR PLATING ON BATTLESHIPS: FRANCE AND GREAT BRITAIN.


The visit of the French squadron under Admiral Gervais to England has
revived in many a nautical mind the recollection of that oft-repeated
controversy as to the relative advantages of armored belts and
citadels. Now that a typical French battleship of the belted class has
been brought so prominently to our notice, it may not be considered an
inappropriate season to dwell shortly upon the various idiosyncrasies
of thought which have produced, in our two nations, types of war
vessels differing so materially from each other as to their protective
features. In order to facilitate a study of these features, the
accompanying sketch has been prepared, which shows at a glance the
relative quantities of armored surface that afford protection to the
Nile, the Camperdown, the Marceau, the Royal Sovereign, and the Dupuy
de Lome; the first three of these vessels having been actually present
at the review on the 21st of August and the two others having been
selected as the latest efforts of shipbuilding skill in France and
Great Britain. Nothing but the armored surface in each several class
is shown, the same scale having been adhered to in all cases.

[Illustration: Armored Surface for Various Ships]

Two impressions cannot fail to be made upon our minds, both as to
French and British armor plate disposition. These two impressions, as
regards Great Britain, point to the Royal Sovereign as embodying the
idea of two protected stations with a narrow and partial connecting
belt; and to the Nile as embodying the idea of a vast and absolutely
protected raft. For France, we have the Marceau as representing the
wholly belted type with four disconnected but protected stations; and
the Dupuy de Lome, in which the armor plating is thinned out to a
substance of only 4 in., so as entirely to cover the sides of the
vessel down to 5 ft, below the water line; this thickness of plating
being regarded as sufficient to break up upon its surface the dreaded
melinite or guncotton shell, but permitting the passage of
armor-piercing projectiles right through from side to side; provision
being made to prevent damage from these latter to engines and vitals
by means of double-armored decks below, with a belt of cellulose
between them. Thus, as we have explained, two prominent ideas are
present in the disposition of armor upon the battleships of Great
Britain, as well as in that of the battleships of France. But, while
in our country these two ideas follow one another in the natural
sequence of development, from the Inflexible to the Royal Sovereign,
the citadel being gradually extended into two redoubts, and space
being left between the redoubts for an auxiliary battery--this latter
being, however, singularly placed above the armored belt, and _not
within its shelter_--in France, on the other hand, we find the second
idea to be a new departure altogether in armored protection, or rather
to be a return to the original thought which produced the Gloire and
vessels of her class. In point of fact, while we have always clung to
the armored citadel, France has discarded the belt altogether, and
gone in for speed and light armor, as well as for a much lighter class
of armament. Time alone, and the circumstances of actual warfare, can
prove which nation has adopted the wisest alternative.

A glance at the engraving will show the striking contrast between the
existing service types as to armored surface. The Marceau appears
absolutely naked by the side of the solidly armed citadel of the Nile.
The contrast between the future types will be, of course, still more
striking, for the reasons given in the last paragraph. But while
remarking upon the paucity of heavy plating as exhibited in the
service French battleships, we would say one word for the angle at
which it is placed. The receding sides of the great vessels of France
give two very important attributes in their favor. In the first place,
a much broader platform at the water line is afforded to secure
steadiness of the ship and stable equilibrium, and the angle at which
the armor rests is so great as to present a very oblique surface to
the impact of projectiles. The trajectory of modern rifled guns is so
exceedingly flat that the angle of descent of the shot or shell is
practically _nil_. Were the sides of the Royal Sovereign to fall back
like those of the Marceau or Magenta, we seriously doubt whether any
projectile, however pointed, would effect penetration at all. We
conclude, then, that a comparison of the Marceau with the Nile as
regards protective features is so incontestably in favor of the
latter, that they cannot be classed together for a moment. In speed,
moreover, though this is not a point under consideration, the Nile has
the advantage. It is impossible, however, to avoid the conviction that
the Dupuy de Lome would be a most powerful and disagreeable enemy for
either of the eight great ironclads of Great Britain now building to
encounter on service. The Hood and Royal Sovereign have many
vulnerable points. At any position outside of the dark and light
 portions of armor plate indicated in our drawing, they could
be hulled with impunity with the