On the Employment of Electro-coppered Cast-iron Cylinders for Printing on Stuffs. By TH. Schlumberger.

(Bulletin de la Société Industrielle de Mulhouse, March 1874, pp. 116-120.)

During the last thirty years, repeated attempts have been made in England to replace the solid copper and brass cylinders used in printing-mills by cylinders of cast iron, covered with copper by galvanic deposit. These attempts have not been attended with the success that was anticipated, and the system has fallen into comparative disuse.

In 1871, M. Théodore Schlumberger presented to the "Société Industrielle de Mulhouse" a Note on the Employment of Cast-iron Coppered Cylinders, and in March last M. Gustave Schæffer reported to the society, which had offered a prize for the best essay on the subject, the progress made up to that time.

Neither the Note of M. Schlumberger nor the Report of M. Schæffer are encouraging. The advantages are sufficiently great to induce perseverance; but the serious difficultes lead to the conclusion, that further experiments should be undertaken from a new starting-point. The copper and brass cylinders employed, in a printing-mill represent a large capital. A new roller weighs between 1 cwt. and 2 cwt., the metal costing 28. to 2s. 6d. per lb., and it can only be employed until, having been successively turned off and re-engraved, its weight is reduced to about cwt. Each re-engraving lessens the weight by about 5 lbs, and the diameter by somewhat more than the depth of the previous engraving. Sometimes, when adapting a roller to a given pattern, or pairing it with another to a given design, much more than this has to be turned to waste. Could cast iron be used as the foundation of these rollers, the saving in capital sunk in these machines would be obviously great. The raw metal would cost less than 1d. per lb., and, when prepared to receive the copper coating, little more than 34d. per lb.

Since 1864 M. Louis Huguenin has coppered a number of rollers, which have been engraved five or six times without any inconvenience. M. Schlumberger asserts that a positive advantage was gained each time the rollers were put into the coppering vats, because the imperfections on the surface of the copper disappeared. He estimates the cost of a cast-iron roller of ordinary dimensions at £4, and the cost of each re-coppering at from 88. to 168.—a price which is capable of reduction.

The difficulties, on the other hand, are serious. In the first place, the saving of cost is less than appears from the estimate of the saving of so many pounds of copper, from the fact that the electrotype copper costs at least five or six times as much as the commercial copper ordinarily used. Next, the adherence between the cast iron and the copper is not sufficient to prevent the latter from being injured under great pressure, and sometimes becom

ing laminated and loosened from the iron. Lastly, a cast-iron coppered roller is more difficult to repair than a solid copper or brass one. When one of the latter gets injured the place is plugged, or the surface burnished up and engraved; with a cast-iron cylinder, however, these processes are difficult, for plugging is attended with the danger of breaking through the coat and leaving the iron exposed, by which the colours or the mordants are altered, while burnishing causes the copper to dilate, and destroys its adherence to the iron.

The process in these experiments was as follows:

After the surface has been turned up true in the lathe, the castiron roller is cleansed of grease by a strong alkaline solution, and washed with an abundance of water, all traces of oxide being removed with a fine file. When this is accomplished, the metallic surface is brilliant, and great care must be taken to prevent the moisture of the breath or of the fingers from coming in contact with it. The cleansed and polished roller is then plunged in an alkaline copper bath, and left during twenty-four hours under the current of five or six elements until the whole surface of the cast iron is covered with a thin but well-adhering skin of copper. This alkaline bath may be composed as follows:-In 12 parts of water dissolve 1 part of sulphate of copper. In 16 parts of water dissolve cyanide of potassium, 3; carbonate of soda, 4; sulphate of soda, 2 parts. The two solutions are mixed after the salts are completely dissolved. Another alkaline bath is composed thus:—Water, 10; ammonia, 3; acetate of copper, 2. Water, 16; cyanide of potassium, 3; of soda, 4; sulphate of soda, 2.

After removal from the alkaline bath, the roller is washed and rubbed with rottenstone. If the iron in any place shows through the film of copper, the roller is returned to the bath until the entire surface is covered. This first coat should be perfect, but as thin as possible. When that result is attained, the roller is well brushed, washed, and rinsed in slightly acidulated water. It is then plunged quickly into an acid bath of sulphate of copper, in which it is left until the deposit of copper is sufficiently thick, being turned partly round each day so as to insure an even deposit. With the current of four elements, and at a moderate temperature, three to four weeks are required to effect a deposit of of a millimètre in thick

ness.

The strength of the solution of sulphate of copper is represented by 20° Beaumé, in which 1 quart of sulphuric acid is added to every 300 quarts of solution, to render the bath more conducting and to assist the dissolution of the scrap copper thrown in to keep up the strength of the bath. R. S..

FOREIGN TRANSACTIONS AND PERIODICALS.

Cultivation of the Sugar-cane in Spain. By M. GRAND.

(Mémoires de la Société des Ingenieurs Civils, April 1874, pp.

266-269.)

The cultivation of the sugar-cane in the 37th degree of north latitude would appear very remarkable to any one unacquainted with the peculiar climatic conditions which render it practicable. That portion of the coast of Andalusia which permits of the growth of the sugar-cane is comprised between the 36th and the 37th degrees of north latitude. At a certain distance from the sea a chain of mountains runs parallel to the coast and forms a shelter from the north winds. The evil effects of a short frost, which occurs once in seven or eight years, are avoided by cutting the cane somewhat earlier in the season than usual. The geographical position of this part of Andalusia enables it to command a great amount of solar heat. As, in addition to a warm climate, a certain degree of humidity is requisite for the growth of the cane, artificial irrigation is resorted to when the natural sources fail. Of the three varieties of canes, that known as American is the best, and is fast superseding the others in all the new plantations. From seven to eight years constitute the productive life of the sugar-cane. The planting is performed by cutting slips. from sound canes of the previous year and placing them horizontally end to end in two rows at the bottom of broad furrows. This operation takes place in May. In October the cane turns yellow, in the following February it arrives at maturity, and it is harvested in the three succeeding months.

Irrigation is indispensable during the dry season, which lasts for three or four months, and as nearly 1,000,000 gallons of water are required for each acre of land, the construction of reservoirs is frequently necessary. The sugar-cane is a very exhausting crop, so that proper manuring of the soil is a subject of great importance. Farm-yard manure, mixed with the refuse of the last crop, is used when the harvest is annual, but when biennial, guano is preferred for the second year. About 12 tons of farm manure per acre is the quantity used. The annual crop per acre averages 20 tons, the biennial 30 tons. The selling price is 368. per ton.

Those engaged in cultivating the sugar-cane in Andalusia are well aware of the limited area upon which it can be grown, and have recently turned their attention towards the introduction of beetroot, as a substitute for the more delicate and susceptible plant. Some experiments have been made with a view to its acclimatisation; so that by causing the crops to come to maturity at different times of the year the working plant and factories would be utilised to a maximum. M. Grand is of opinion that by judicious management, in advancing one crop and retarding another, this object might be effected.

C. T.

On the Multiple System of Signalling.

(Annales Telegraphiques, Sept.-Oct. 1874, pp. 187-224.)

In every system of transmission, the line wire remains unoccupied during that fraction of time between the signals which is more than necessary for the discharge of the wire. The consequent loss of time becomes considerable where the rate of transmission depends upon the quickness of manipulation; because the time required for the mechanical operation of signalling is greater than that required by the current to pass and reproduce the signals: e.g., the greatest number of dashes that an operator can send per second is five, while the wire can take and reproduce distinctly a much larger number.

To utilise these intervals is the aim of the Multiple System; which term implies the connection of more than one communicating post through the same line wire, each working simultaneously with, but independently of the other.

Take, for instance, two places communicating by the Morse system, and sending dots and dashes; between each of these signals the wires, being free, may be detached from the first pair of instruments, and when connected with a second pair, may send during the time of contact a dot or a dash.

If each pair of instruments has an interval sufficient for the longest signal (a dash), two distinct messages can be sent in the same time, these messages being not simultaneous, but successive.

Another method consists of spacing regularly, not the elementary signals, but the letters, by allowing for each letter an interval long enough for the longest (ch).

If an interval sufficient for the longest signal or letter is allowed for each, and between two successive signals an interval is left sufficient for n -1 dashes, or between two letters an interval for n-1 times the longest letter in the alphabet (ch), then during each part of an interval sufficient for a dash or ch, the terminals can be connected with a new pair of instruments, and the transmission of n distinct messages may be obtained in the time required for the single original message, while at the n communicating places, or posts, each sender and receiver will have at their disposal an amount of time which is at least n times longer than that required for the passage of the currents.

In principle, this system of multiple signalling is inferior to that of prepared messages, in which a complete separation is made between the personal work and the signalling proper, and where, in fact, each signal only takes up the time absolutely necessary for the passage of the currents. In the multiple system, the dot takes as long as the dash, and the shortest letter as long as the longest; the system of prepared messages therefore must be more economical of time, in the proportion of 2 to 1, that is of the longest letter (ch) to one of mean length (u).

To make the most out of the multiple system, this subdivision of time must be the shortest possible, and the number of signals passed during it the greatest. Suppose one clerk makes five dashes in a

FOREIGN TRANSACTIONS AND PERIODICALS.

second, he will take of a second to make the longest letter, and will send seventy-five letters a minute; each subdivision, therefore, would be equal to of a minute. The number of distinct signals that can be transmitted in that time depends upon the electrical state of the line. Suppose the number of dashes the wire will transN

mit, clearly, per second to be equal to N: then

5

of clerks who can work at each end of the same wire.

is the number

Although the system of multiple signalling is disadvantagous, as compared with prepared messages, in so far as it requires an absolute synchronism between the corresponding stations, yet it possesses advantages in the facility given to each clerk for repeating, rectifying, and altering each individual message; while the manager is enabled more easily to proportion his staff to the varying requirements at different hours in the day; and there are greater facilities for corresponding from one central station to several outlying stations.

In the two machines known as the Rouvier and the Meyer, there must be at each end of the wire commutators moving in absolute synchronism, and the personal work, or signalling, must be In the Rouvier subordinate to the motions of these commutators. system the synchronism is obtained by pendulums, one at each end of the line, of equal length, oscillating between electro-magnets, which are actuated by make and break arrangements. The action is briefly as follows; each pendulum, towards the end of its stroke, makes a contact, by which the current in the line wire closes local circuits. These acting on an electro-magnet at each end, attract each pendulum during the fraction of its course which is reserved for correcting any departure from synchronism, until, by a second simultaneous contact of the pendulums, the line wire is insulated, the local circuits are opened, and the pendulums free to fall. But if this second contact of the two pendulums is not simultaneous, a current still passes in the line wire, the local circuit remains closed, and that pendulum which is in advance is retained till the other has come up to it.

Suppose it is required to work Rouvier's system of multiple signalling between two stations, and, for simplicity, let it be

X 6. с

FIG. 1.

2

supposed that there are only two independent communicating posts. Take a plane, as shown in Fig. 1, parallel to the plane of