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.

[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 tele graph, 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!

Zink Thread.-The Moniteur Industriel announces that an important discovery in the manufacture of zink thread has been effected by

been able to produce zink threads of any diameter, of great suppleness, and presenting all the qualities of an 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.

cher, who, after many essays, has at length Bou

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 engineering 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.

screw

IN screw-propelled vessels, the intervention of multiplying wheel-work between the engine cranks and the scre propeller, in order to produce a suitable rapidity of motion in the latter (which is the plan adopted on board the Rattler,) is admitted on all hands to be exceedingly objectionable, as well on account of the great increase of weight, friction, and noise, thus occasioned, as of the extreme liability of the wheel-work itself to breakage and derangement. But with the best marine engines, as hitherto constructed, whether beam or direct-action, a screw propeller can be worked in no other way; not because there is any difficulty in connecting the pistons with the propeller shaft, or any objection to increasing the number of strokes of the piston, but because, if the pistons were to move as fast as the propellers, the cylinders must also be exhausted as fast, and this, with such slide valves and working gear as are now commonly in use, is impossible. An important practical problem remained to be solved, which was this-how to fill and clear the cylinders so quickly, that the pistons might be allowed to move as fast as the propeller, and the engine be started, reversed or stopped, with as instantaneous effect as when worked at the ordinary slow rate. Difficult of solution as this problem is, we are glad to say it has been solved most successfully, by the improved arrangements which form the subject of our present notice.

Fig. 1 is a lateral elevation of one of a pair of steam engines, embodying these arrangements, recently constructed by Messrs. Maudslay and Co.; fig. 2, a horizontal plan; fig. 3, a vertical transverse section; and fig. 4, a transverse elevation of fig. 3.

EE are the steam cylinders; F F the condensers, parts of which serve as supports for the cylinders, and other parts extend horizontally to the air pumps HH; P P are the main axes of the revolving cranks placed beneath the central lines of the cylinders, and supported in bearings formed in standards V V, which stand up upon the lower parts of the condensers, and extend up to the bottom of the cylinders; O O O O, are the main revolving cranks fastened on the ends of the main axes; P P, and N N are connecting cranks fastened on the two ends of

the intermediate axis Q, which is in the same line with the axis P P, and which connects the two engines together; X X are the bearings for the axis Q, both of which are affixed to a bed plate B, which is supported on, and bolted down to suitable sleepers at the bottom of the vessel; the lower parts of the condensers F F, of both engines, are supported on, and bolted down to the same sleepers, so as to fasten both engines, and the bearings X X for their intermediate axis Q, firmly in their relative positions as they appear in the engravings; L is another con necting crank on the foremost end of a long axis Y, which extends towards the stern of the vessel, and the aftermost end of Y is coupled to the foremost end of another piece or length, W, of such axis, which latter piece passes through a stuffing-box at the stern to the outside, and has the revolving propeller Z, fig. 1, fastened on the aftermost end of it. (The coupling, it will be observed, which connects the aftermost end of the axis Y; the foremost end of the prolonging piece W, is made so as to be capable of being disconnected when the vessel is intended to be impelled by sails, without using the engines.) The ends of the axis Y are sustained in bearings, whereof one is seen at R, and is similar to the bearings X, and is supported upon, and bolted down to the sleepers before mentioned. The several axes, P, Q, P, Y, and W, range exactly in the same line, one with the other, and are all connected together by means of the crank pins, which are fastened into, and project out from the main cranks, O O O O; the ends of which crank pins enter into the holes at the ends of the connecting cranks, N N and L, and by that means, together with the coupling box already mentioned, which connects the pieces Y and W, the said several pieces of the axis constitute, as it were, one long continuance of revolving axes, by which the power exerted by the two engines within the vessel is transmitted to the revolving propellers Z, at the stern of the vessel, in the water outside. The requisite revolving motion of the said line of axes is communicated thereto by the connecting side rods, M M, M M, one at each side of each cylinder E E, with their lower ends fitted upon the crank pins of the main cranks O O O O, and with their upper ends fitted upon the ends of the horizontal cross heads o o, which are fastened by their middles across the upper ends of the vertical piston rods n n, which move up and down through stuffing-boxes in the centres of the covers of the cylinders E E; the pistons J J are fastened on the lower ends of the piston rods n n, so that when those