said, to buy the colour ready made from other manufacturers, who devote themselves exclusively to this. The antimony appears, in this case, merely to give brilliancy to the glass without colouring it at all.

According to the director of one of the glass works in the neighbourhood of those of Bohemia, a very beautiful ruby colour may be obtained in the following way :Dissolve by heat one gramme (15.4 grains troy,) of fine gold in an aqua regia composed as follows,-12 grammes nitric acid, 12 grammes muriatic acid, and 1 gramme sal ammoniac. Again, dissolve by heat 1 gramme of tin, in an aqua regia composed of 20 grammes nitric acid, and 6 muriatic acid; then pour the two solutions into a large vessel containing already 500 grammes of clear water, and mix them intimately by agitating the vessel after corking it. The red precipitate of purple of Cassius, which forms, is washed and dried with care. A peculiar glass is then prepared by mixing together 40 parts of very pure quartz pulverised, 16 parts of nitre, 8 parts of borax, 1 part of white arsenic, 1 part of cream of tartar, finely pulverized and sifted through silk; and a greater, or less quantity of the purple of Cassius, according as you want a more or less deep colour. This mixture is introduced into a clay crucible made expressly, not glazed, and of about the capacity of 5 quarts, or else in an ordinary glass pot, then heated in a glass furnace, or in a small furnace made expressly for it, taking care to stir the materials continually until they have attained a dull red heat. The crucible is then covered, and the heat continued for some time. When the mass is perfectly melted, and gives no more bubbles, the crucible is removed, and after suffering it to cool for 4 or 5 five hours in a cellar, it is broken, and the glass obtained separated with care from the impurities which it may contain; it is then ground and sifted. If now there be melted together in a small crucible placed in the glass furnace, the following mixture: 128 parts of pure quartz pulverized, 64 parts of nitre, 3 parts of borax, and 3 parts of white arsenic; and the glass thus obtained poured into cold water, then ground, and passed through a sieve, then mixed with the coloured glass prepared as above, and melted in a glass crucible, a glass will be obtained, which, worked up into articles of a thickness not exceeding 0·16 to 0.2 inch, takes a beautiful ruby colour when exposed to the smoke obtained from burning fir, or that of alder.

Bohemian Ruby-Red.-They prepare besides, in Bohemia, a peculiar ruby colour, which is also employed in cakes, and has received the name of Bohemian Ruby. It is prepared by melting together quartz pow

399

dered and fritted 100, minium 150, potassa fritted 30, borax fritted 20, sulphuret of antimony 5, peroxide of manganese 5, fulminating gold rubbed in with oil of turpentine 5. If a little more fulminating gold is used a magnificent ruby colour is obtained.

Fulminating gold is obtained by precipitating the solution of gold in aqua regia by ammonia, and stirring the liquid for some time. The precipitate is then collected upon a filter, and washed rapidly with water boiled, and rendered slightly ammoniacal, then dried at a very low temperature. There is thus obtained a powder of a deep brownish yellow, very explosive, and of which the manipulation requires great precaution.

Ancient Red called Kirschroth (cherryred.) This colour is generally employed in cake; it is procured by the use of sub-oxide of copper, which is kept in the state of suboxide by the addition of an equal quantity of protoxide of tin. When it is desired to pass the colour to a fiery red, a little oxide of iron is added. The proportion of oxide of tin must then be reduced, and it may entirely disappear, as in a very beautiful antique red glass, found at Caprea, in the villa of the emperor Tiberius, the analysis of which gave, Silica

Protoxide of lead
Suboxide of copper
Peroxide of iron.
Alumina....
Lime

71.

14.

7.5

1.

2.5

1.5

97.5

* Sometimes the glass is merely coloured with the oxide of copper, and then after the articles are finished they are smoked, which gives them a deep red colour.

Blue. The azure blue colour is obtained by the oxide of copper alone, cobalt blue by the oxide of cobalt, or smalts.

Amethystine Violet.-This colour is obtained by the oxide of manganese, mixed with a little nitre.

Yellow. There are five distinct yellows which are prepared as follows:

1. Topaz Yellow.-Prepared with charcoal dust.

2. Antimony Yellow.-Prepared with a mixture of glass of antimony and minium.

3. Orange Yellow.-Prepared with glass of antimony, minium, and a little oxide of iron.

4. A Peculiar Yellow.-Very expensive, which is prepared with chloride of silver, and is only applied in a very thin layer, as a sort of enamel, the glass must then be smoked, in order to make the colour appear.

5. Greenish Yellow.-Which produces a fine effect in day light, but which appears of

a dirty yellowish white by the light of a lamp, or candle. This yellow is prepared with the yellow oxide of uranium of commerce, but since this last contains traces of iron, the yellow glass obtained presents almost always a light green tint upon its edges. Green. There are four distinct greens :1. Grass Green.-Which is obtained by the oxide of chrome, or a mixture of glass of antimony and oxide of cobalt.

2. Bottle Green. - Prepared with protoxide of iron.

-Prepared

3. Ancient Emerald Green. with oxide of copper mixed with a small quantity of finery cinders.

4. Modern Emerald Green.-This colour, which is far more beautiful than the preceding, is prepared with a mixture of oxides of nickel and uranium.

Black. Is prepared with peroxide of manganese, oxide of copper, oxide of cobalt, in equal parts; or else with a mixture of finery cinders, peroxide of iron, oxide of copper, or cobalt.

Hyacinth.-The hyacinthine colour is obtained with a large quantity of red oxide of iron, and the oxide of nickel.

They

Sir,-In your Magazine, of Saturday, May 24, p. 351, your remarks on the rotary engines in the Janus are quite contrary to facts as regards the Government. have had one engine on this principle at work in Portsmouth Dockyard upwards of two years, made by us, and it was on the report of their own engineer, that they decided on ordering those in the Janus, and which, I will add, are proceeding satisfactorily.

Believe me, Sir, your obedient servant, CHARLES ROBINSON. (Late Bramah and Co.)

Pimlico, June 3, 1845.

[We gave the Times as our authority for the failure of the engines in the Janus, and we have never seen in that journal any contradiction of its statements on the subject. We have this farther reason for believing them to be true, that persons of verity, who have been on board the vessel and seen the engines (since they were tried,) have told us the same thing. What to make, therefore, of Mr. Robinson's "proceeding satisfactorily" we know not. We are puzzled.-Ed. M. M.]

NOTES AND NOTICES.

British and American Magnetic Telegraphs.-We quote the following from the Pennsylvanian:-" A

comparison of the two systems of the magnetic telegraph, as in operation in this country and Great Britain respectively, leaves no room for doubt as to the great superiority of our own. We have seen a series of plates representing the British system and the mode of working it. It is complicated in its structure and less efficient than Mr. Morse's. The operator stands with an index before him, by which he is to guide his movements; and by means of a corresponding index at the other end of the line, the characters or symbols are pointed out as the magnetic influence operates. It is thus requisite that observers be always present at both ends of the line, and if the observer is not watchful he may miss some of the information indicated by the telegraph. The system of Professor Morse is more simple in its construction. It works with more facility and certainty, and inscribes the information it communicates in permanent characters upon paper, so that if one is not watching at the moment, the record of every word transmitted by it is to be found faithfully preserved. The operation of this system along the line between Washington and this city has proved its wonderful powers to the astonishment of every beholder."

State of Knowledge in High Places.-The Morning Chronicle says, that "one of the select members' of a Railway Committee, last week, on the second day asked the counsel for a Bill, What was the meaning of a gradient;' and a Lord of the Treasury is reported to have been innocent of the meaning of a curve !""

A Spoke in the Wheel.-The Pope has prohibited the introduction into his territories of two of the greatest material improvements of modern timesthe railway system, and the gilding of metals by galvanism!

an

Zink Thread.-The Moniteur Industriel announces that an important discovery in the manufacture of zink thread has been effected by M. Boucher, who, after many essays, has at length been able to produce zink threads of any diameter, of great suppleness, and presenting all the qualities of excellent metal thread. In all cases where great tension is not required, this thread can be substituted with advantage for that of iron, brass, or copper. The price of zink has doubled during the last few years, but, notwithstanding, M. Boucher vends his thread at a lower price than the galvanic iron thread, and considerably less than brass thread.

The "Queen of the French," is the name given to a new-mail packet which was launched on Thursday last from the building-yard of Messrs. Ditchburn and Mare, at Blackwall. She is the property of the South-Eastern Railway Company, and is intended to ply as a mail-packet between Folkstone and Boulogne. Her form of build is of the same character as the Queen of the Belgians, which has so much distinguished herself; her hull is divided into five compartments, so as to render her perfectly secure, in the event of meeting with any accident at sea. Her length is 145 feet, width 22 feet, draught 6 feet. She will be fitted with engines of 120-horses power, on the annular cylinder principle, by Mr. J. Maudslay, the patentee, similar to those which have so well succeeded in the Princess Alice. Her speed is anticipated to be very great, and against a strong head wind and tide her engines and floats are so arranged that they will be constantly in motion and make full 17 miles an hour. A singular circumstance connected with her engines is, that when they were first projected by the patentee they were almost universally condemned by the engincering world. Messrs. Ditchburn and Mare, however, were induced to build the Princess Alice for the express purpose of trying them, and they have eminently succeeded. The Queen of the French has been on the stocks about three months, and will be placed on her station in about a month. -Times.