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TYPE-I'RITLVG BY TELEGRAPH.'

so whether we consider the ultimate result, that is to say,

the printed letter, or merely the alterations produced in ONE of the most interesting papers read during the last the space relationship of the various parts of the printing

session of the Institution of Electrical Engineers was mechanism which causes that mechanism instantaneously Ex that by Mr. Donald Murray on setting type by telegraph. print a particular letter. Thus we may say that what a Strictly speaking, the title of the paper is something of a type-writing telegraph has to do is the following :-it has misnomer, as the apparatus described by Mr. Murray was to receive a message and translate it into a series of time constructed for type-writing rather than type-setting; but or magnitude signals, to transmit these signals plectrically as the principle, is equally applicable to the latter process, over a wire, and to re-translate them into a series of space it is unnecessary to be too critical. This is specially the signals. case as the instruments and method were originally de- ! We have had occasion during recent years to describe

several systems of telegraphy which aim at doing much the same thing as the Murray telegraph attempts, and it is of interest to compare the transmission methods used in these. Thos in the telautograph (see NATURE, vol. Ixiv. p. 107) the actual handwriting of the original message is transmitted and reproduced, and this is done by a combination of space and magnitude signals. Two wires are used, and current pulses of varying magnitudes sent along them which reproduce ar the receiving end the motion of a pea at the transmitting station. Here the time element of the signals has no effect, and a letter is reproduced equally if it be traced in one second or in one hour. In the Pollak-Virag system (see NATURE, vol. Ixiv. p. 7) the telegraphic signals produce the

motion of a beam of light which reFig. 1.-Keyboard Perforator with cover removed.

cords in Roman letters the message

transmitted. In this system the telesigned for the automatic telegraphic operation of linotype graphic signals differ from one another in their space machines, and it was only because commercial consider- relation and their duration. In the Murray system the ations indicated the greater importance of the solution of signals differ from one another in their time relation. the problem of telegraphic type-writing that attention was i We have pointed out that the first process is the transmore particularly devoted to this question.

lation of the message into a series of time signals, and The problem which has to be solved is one of consider- for this purpose a time signal alphabet has to be chosen. able complexity, as will readily be realised when its 'Though this may at first sight seem a matter of secondary essential characteristics are considered. A message handed importance, it is in reality hardly too much to say that in at the transmitting station has to be translated into a upon the suitability of the alphabet selected will depend, series of signals which can be telegraphically transmitted more than upon anything else, the chances of success over a single telegraph wire. These signals, on arriving at the receiving station, must actuate a receiving mechanism in such a manner that a particular set of signals produces a certain definite movement of the mechanism; thus the signals corresponding to the letter "a" must cause the striking (or equivalent) of the typewriter key “a," the signals corresponding to a notification of the end of a line must cause the shifting of the type-writer carriage ready for a new line, and so on. Now it is obvious that the signals as they are transmitted over the telegraph wire can only differ from each other by virtue either of their time arrangement or their magnitude. Each set of signals (corresponding to a letter) must be made up of one or more pulses of current, and one letter can only be distinguished from another by virtue of the pulses for the one being different in magnitude from

Fig. 2.--Single-line Transmitter. those for the other, by their following one another at different intervals of time, or by their lasting for different periods of 'l of the system. This fact has been thoroughly realised bi time; of course, also, a combination of any two or of Mr. Murray and others who have worked upon this all three of these may be used. It is not possible for problem, with the result that an alphabet has been finalls the telegraphic signals to be differentiated in space devised which seems to possess in the greatest degre unless more than one wire is used to connect the two i possible all the more important advantages. In it ever stations. It is equally clear that the distinction between | letter or other signal which has to be transmitted is to the signals in their final form is one of space, and this is presented by a series of five time signals; the alphabet is 1 "Setting Type by Telegraph." By Dona'd Murray. (Journal

therefore an “equal letter alphabet," that is to say, each of the Institution of Electrical Engineers, vol. xxxiv., pp. 555.

letter is composed of the same number of signal units (five 1905).

in this case). The average number of units per letter is, of

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course, five; in the Morse alphabet the average number is corrections; these are made by punching five holes, thus thirteen; there is therefore an apparent advantage in time blotting out all the holes already punched, this signal (of over the Morse code, but this may be more apparent than five holes) leaving the receiving mechanism unaffected. real, as the unequal length of the letters in the Morse! It is thus possible to wipe out any part of the message code enables the shorter ones to be chosen for those letters incorrectly written on the tape, and so produce à tape occurring with the greatest frequency (such as E and T), which will give an absolutely correct message when transso that the average number of units per message may be mitted ; this is facilitated by the fact that the operator

can see the tape as it is perforated,

letter by letter. The speed at which TRANSMITTING STATION

RECEIVING STATION

this perforator can be worked is

about 120 letters (twenty words) a MOTOR - (PHONIC-WHEEL & VIBRATOR)

minute. The transmission can be

carried on five or six times as TRANSLATOR

rapidly, so that five or six operators working at these perforators can produce enough tape to keep the

transmission line full. LECTOR

The automatic transmitter is SCUCTOR

shown in Fig. 2, and diagrammatically in Fig. 3 (collector). The

tape is fed forward in the usual way TRANSMITTER

by the star-wheel 15, passing across the end of an upright rod 1. This rod is pivoted as shown to the system of levers which oscillate

about the centre 4, being kept in DISTRIBUTOR PUNCHING

oscillation by the eccentric wheel ŝi and making one oscillation for every

unit on the tape. If this unit is a RECORDER

hole, the rod i enters this hole, the end 2 of the lever 2-9 is raised and the end 9 lowered, whereby the oscillation of the lever 3 brings the end 9 against the bar 11, thus pushing the contact lever 13 against contact 18. Here it remains until the next oscillation, and if this is the

same as before, due to a second FIG. 3. —General Diagram of Murray Automatic Printing Telegraph System.

hole in the tape, it is not disturbed.

It will thus be seen that successive less than in an equal letter alphabet having a smaller signals of the same kind (either successive holes or average number of units per letter. Thus experience has successive spaces) are transmitted, not as intermittent, shown that the actual average number of units per letter but as continuous signals. But if there follows a space with the Morse code is only eight instead of thirteen. It in the tape the rod I cannot rise to its full height, must be remembered, also, that the Morse code is intended the lever 2-9 is kept down at the end 2 and raised at primarily for hand signalling, and consequently when time the end 9, which comes in consequence against the rod intervals are used the difference between any two which 10 and forces the contact lever 13 over against contact have to be distinguished manually or by ear must be fairly | 19, thereby breaking the punching current and sendgreat. Thus the Morse dot consists of one unit, the Morse | ing spacing current into the line. The whole apparatus dash of three; were two units used for the dash instead is driven by a phonic wheel motor in the usual way, the of three, the distinction between the dash and dot would vibrating reed 23 sending currents alternately to the not be sufficiently marked. With machine telegraphy, on magnets 24 and 25. which keep the armature 26 in rotathe other hand, there is no need to make such a great tion. This is geared directly to the star-wheel 15, which differentiation between the signals, as time intervals of has ten teeth, and is itself geared in the ratio of 10: 1 one, two, three, and more units can all be distinguished, to the eccentric wheel 5. so that the latter makes, and in consequence it is possible to devise a shorter as already stated, one revolution for every unit of the alphabet than the Morse code. It is not to be denied, I tape. however, that the use of a new alphabet is undoubtedly Now let us follow the message to its arrival at the a disadvantage from the practical point of view, as it has to be learnt by the operators. This drawback is minimised by the fact that the operator does not print

P
A
R :

S ; each signal separately as in operating a transmitting key ; but it is nevertheless desirable, if not essential, that he should be able to read the message when printed on the

640 00 00 000 000 000 0000 0 0 0 0 0 0 0 0 0:0) transmitting tape.

00 000 To turn now to the apparatus used in the Murray system ; the first operation, as in all automatic telegraph systems, is to punch the message to be transmitted on a paner strip or “ tape.” This is done by means of a keyboard instrument of the ordinary type-writer form shown, with the cover removed, in Fig. 1. On the tape will be noticed a double row of holes, which can be seen more distinctly in Fig. 4: the row of small holes serves

F16. 4. only to feed the tape forward, both in this machine and in the transmitter : the larger holes are the signals punched in the tape. The actual perforator can be seen receiving station, where the signals are caused to produce in front; it is worked by an electromagnet which a second perforated tape, the exact duplicate of the first, punches the necessary holes on the forward stroke and by means of the mechanism grouped together in Fig. 3 moves the tape one letter space (five holes) forward on ' under the title " distributor." The tape is fed forward its back stroke. On the right can be seen a lever which unit by unit by means of the spacing magnet which enables the tape to be pulled back letter by letter to make operates the escapement 31, and holes are punched in the tape by the punch 30, which is operated by the punching intermittent current impulses to the spacing magnet due magnet. If the circuits of these two magnets are followed to the closing of contact 32. Line 3 shows the main out it will be seen that both are controlled by the vibrating line signals which, as pointed out in explaining the method reed 34 in such a way that they operate alternately accord in which the transmitter acts, are continuous and not ing as the reed is against contact 32 or 33. It will further intermittent, Line 4 shows the interruptions in the circuit be seen that the punching magnet is also controlled by the of the vibrator magnet caused by the vibration of the punching relay 27, the circuit being open in the position reed of the governing relay which occurs at the beginning shown, and closed when the reed 41 is against contact 44, and end of every signal in line 3. In line 5 are the actual i.e. when punching current is coming through the main current pulses in the vibrator magnet due to the closing line and punching relay. It will be noticed at once that of contact 40. These are shown in step at the beginning, the distributor cannot work properly unless the tongue 41 but gradually falling out of step, whereby, as will be of the punching relay is in synchronism with the reed 34. seen, they are diminished by the interruptions shown in To obtain this synchonism is the object of the governing | line 4, and are thus automatically brought back into step. relay 28, which is operated by the line current. The The only remaining operation is to use the tape 45

(Fig. 3) to work either a type-writer or a type-setting machine. The Murray printer with the type-writer removed is shown in Fig. 5, and diagrammatically in Fig. 3. It will not be necessary to describe it in detail; the principle is that of the ordinary lock and key. The tape is fed forward letter by letter by means of the star-wheel 46; the re. ciprocating shuttle 47 carries a die block, which allows the five rods 48 to pass through the perforations in the tape when these are present. Accord. ing as one or more of these rods passes through the tape, a particular set of slots in the combs, 49, attached to the rods is brought into line, the corre. sponding lever 50 is pulled into the channel thus formed, and the corresponding type-writer key is depressed.

The complete set of Murray apparFig. 5.- Murray Printer with Typewriter removed.

atus is shown in Fig. 6. On the extreme right is the perforator, next to

it on the left the automatic transtongue of this relay vibrates between the contacts 42 | mitter, then on the same table the distributor in front and and 43 ; when it is in contact with either the circuit of the relay's behind. The translator and type-writer are on the vibrator magnet is closed, but during its passage the small table at the left. We have only been able to give from one to the other this circuit is opened. If this a brief description of the most important features of this occurs whilst the contact 40 is open it can obviously have very ingenious system; there are numerous points of no effect on the oscillations of the reed, but if it occurs detail which space does not permit us to describe. The whilst this contact is closed it has the effect of diminish- system has been on trial for some time both in this

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ing the duration of the current in the vibrator magnet. | country and abroad, and has met with considerable succes, The reed 34 vibrates against two springs 36 and 37, so it is now in use on several English lines. There can that its time of vibration is capable of great control by be no question after the perusal of Mr. Murray's paper the magnitude of the current in the vibrating magnet. that it possesses many advantages over its forerunners By setting it so that its natural speed is a little too which should enable it to survive. It is stated that the high, it is possible by means of the controlling action of automatic part of the apparatus can be run perfectly up the governing relay for perfect synchronism to be obtained. to 200 words (1200 letters) a minute, but that no typeThe action will perhaps be more readily understood by writer will stand the strain of being run at this speed, a the diagram, Fig. 4. This shows a piece of the trans maximum of 120 words being all that is allowable. It is, mitting tape at the top punched with the signals for the however, obviously possible to run the automatic part at word “ Paris." In line I are shown the current im top speed if necessary, and use two type-writers at the pulses to the punching magnet due to the simultaneous receiving end in the same way as at the transmitting end. closing of contacts 33 and 44. In line 2 are the regular !

MAURICE SOLOMOX.

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THE PERCY SLADEN EVPEDITION IN H.M.S. sand here and there. Indeed, our evidence points to the

O impossibility of any upward growth being in progress SEALARK. THE CHIGOS ARCHIPELAGO.

between the different Chagos banks, and to the probability OCR arrival in Mauritius on August 5 completed the l of considerable current being felt even at 500 fathoms.

first half of our cruise in H.M.S. Sealark, together' The reefs of the Chagos are in no way peculiar save with all our work directly connected with the Chagos in their extraordinary paucity of animal life, to which I Archipelago. This work may be divided under two heads, referred in my last letter. Green weed, too, of every oceanography and biology. The former has been carried sort is practically absent. However, this barrenness is out mainly by Commander Boyle Somerville and his officers amply compensated for by the enormous quantity of nulliin view of the scientific objects of the expedition, but at porej (Lithothamnia, &c.), incrusting, massive, mammillated, the same time it is all of practical value for navigation, columnar, and branching. The outgrowing seaward edges in these waters. In many respects it has been of a of the reefs are practically formed by their growths, and singularly arduous nature; surveys by camping parties and i it is not too much to say that were it not for the deep soundings from the ship have been carried on simul- abundance and large masses of these organisms there taneously, together with numerous observations on the would be no atolls with surface reefs, &c., in the Chagos. tides, currents, sea temperatures, &c. To a considerable! The lagoon shoals of Egmont are covered by them, and degree it and all the work has been hampered by the alone reach the surface; having once done so they die heavy weather, which, contrary to all expectation, we have' and become hollowed out in the centre, finally resembling experienced, winds from south to east with heavy, con- | miniature atolls. fused seas, partially induced by the comparatively shallow waters of the Chagos Archipelago, and partially due to the current, which set in an easterly direction (against the wind) during the whole time we were in the group. It is almost too soon to attempt to sum

sa o zio gore so 5 oss marise any of the results of the cruise, but the soundings taken on our course from Ceylon to the Chagos and from the latter to

50 150 tonn o erdo@quello Mauritius show that the archipelago is closely surrounded, both to the north and west, by the 2000-fathom line, and that there is at the present day no trace in the topography of the Indian Ocean of any former connection of the group with either the Maldives or the banks on the Seychelles-Mauritius line. The

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Lagle a depth of 8oo fathoms in an ocean of an

* Chagos Bank 2856 average depth of 2300 fathoms. Previously

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there were no bottom soundings between the
banks and shoals of the group, but now a
large series (more than 100) have been run,
showing depths of 400 fathoms to 8oo fathoms
between the individual banks; from most of
these a sample of the bottom has been
obtained.

Broadly speaking, the Chagos group may be Bic Bank said to consist of three atolls to the north

1806.30. ** 2 (Salomon, Peros Banhos, and Blenheim), the Great Chagos Bank in the centre (60 miles by

XO 200 00 miles), and to the south two atolls, Diego Garcia and Egmont, besides certain submerged banks both to the north and south. Of these, H.M.S. Sealark has re-charted Salomon and Conturions parts of Peros Banhos, while Cooper and lot have in addition examined the southern atolls.

l

O XO Salomon was very carefully surveyed, our intention being to make a comparison between

Fig. 1.--Chart of the Chagos Archipelago. its condition at the present time and when Powell's chart was made in 1837. The latter chart, however, proved to have been so carelessly | In such a large group the conditions of the encircling drawn that any close comparison is, I fear, useless, i reefs against the lagoons naturally vary very considerbut the new chart should be of great value when it is ably. In general their inner edges reach the surface, and possible to re-examine the atoll at some future date. in the more open atolls the lagoon slope to 10 fathoms Its section lines show that it arises in the last 400 fathoms closely resembles the seaward slope. The bottoms of the by similar slopes to those of Funafuti, but it is a much lagoons are bare, rock, hard sand or mud, with shoals simpler atoll, having only one passage, and more than half | arising precipitously here and there, built up by a few its reef crowned by land. Our numerous soundings and species of coral, but largely covered by Xenia and Sarcodredgings on its slopes leave no room for doubt but that phytum (as also are the only two submerged banks, Wight its present reef is extending outwards on every side on ! and Centurion, which we examined). Diego Garcia lagoon its own talus, in fact, that the steep found round it (and, ! differs somewhat owing to its being almost completely indeed, most atolls) is, in this instance, simply the slope surrounded by land. It has perhaps the most varied fauna at which coral and other remains from the reef above come in the group, and alone gives definite evidence of enlarging to rest in the water. Its face was everywhere singularly in every direction. Everywhere the land is entirely of coral barren; Lithothamnion, Polytrema, and, of course, reef- origin. Diego Garcia shows signs of a recent elevation corals were not obtained below 50 fathoms. Further out, I of a few feet, the present single island having been formed at 250 fathoms and over, the bottom was smooth and by the joining up of a series of separate islets on an barren; the lead constantly failed to bring up any samples, elongated reef. The kuli or barachois (large shallow lakes) while the somewhat broken and dented, but almost empty of the same island owe their origin to the same elevation, dredges gave the idea of bare rock with a little muddy I though elsewhere in the group they are generally due to

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the successive washing up of beaches from the sea, en- brigge Fletcher has sorted the insects
closing areas of the reef. On the whole, there is singularly 110 species, most of which are probabl
little change since the survey in 1837, and my impression the best season for the group would be
is that Chagos has been for a long time an area of rest, and damper north-west monsoon. Onth
and that the present condition of its reefs is mainly due fauna and fora is much what one wou
to agencies still in action.

regarding the Chagos as a group of purel
We have now examined the marine fauna in Salomon, We expect to leave Mauritius toward
Peros Banhos, Diego Garcia, and Egmont, and I would for Cargados, Agalegas, and the submerg
again lay stress on its comparative paucity and lack of the Seychelles. Our cruise will be largely
variety as compared with the Maldives, Fiji, or even but the examination of Agalegas should
Funafuti, though many of the forms are very common. Meanwhile, Cooper and I hope to see some
In short, its general character is rather that of the round Mauritius.
temperate than of the tropical zone.

J. STANLEY G The land fauna is largely dependent on the flora, and the latter, except on small isolated islets and selected positions, has been destroyed to allow of cocoanuts being

IRON AND STEEL INSTITUT planted. The shores are everywhere fringer with Scaevola FOR the first time the autumn meeting of the koenigii and Tournefortia argentea, both covered with a 1 Steel Institute was this year held in Shel climbing bean. Behind these there was originally a forest elaborate programme of visits to works and social formed of immense mapon (Pisonia ca pidia) and takamaka was arranged, and no less than 1500 members (Calophyllum inophyllum), with a few cocoanuts, Barring were present, including members from all part tonia, banyans, and other smaller trees, and an under. world. The opening meeting was held at growth largely consisting of immense Asplenium and other university on September 26 under the presidency

R. A. Hadfield. Addresses of were delivered by the Lord May Master Cutler, the Vice-Chand the University, Colonel (chairman of the reception mittec), and by the president Sheffield Trades and Labour on behalf of the working men Hadfield, in reply, thanked the tion committee for the admi work it had done, and gav interesting historical review Sheffield steel trade. Incidentall mentioned that the membership Iron and Steel Institute had now to 2200. After the reading of minutes of the last meeting by secretary, Mr. Beanett H. Aro and the transaction of other roul business, the papers submitted read and discussed. In the first pe taken Prof. J. O. Arnold deser the department of iron and metallurgy at the University of Sheffield. The main object borne in mind in designing the laboratory was the erection on a manufacturing scale of plant producing steel by the crucible, Bessemer, and Siemens processes.

Prof. J. O. Arnold and Mr. A

McWilliam next contributed an Fig. 2.- Lithothamnia on the Seaward Reef of Salomon Atoll, Chagos Archipelago

important paper on the thermal transformations of carbon steels. For the

research three steels were selected ferns and Psilotum, herbaceous dicotyledons being con- saturated with 0.89 per cent. of carbon, unsaturated fined to the more open, dry, sandy, and stony parts; with 0.21 per cent of carbon, and supersaturated mangroves and Pandani are, curiously enough, not found. with 1.78 per cent. of carbon. In the case of the usWith the assistance of Dr. Simpson, we have collected the saturated steel, the authors find that above Ar 3 (810° C. flora of each of the atolls, obtaining more than 600 speci the ferrite and hardenite are in mutual solution as a mens, about 140 species, of which probabiy only half are homogeneous mass. The Ar 3 change is accompanied by indigenous.

a segregation of the two constituents, which, if the cool of mammals there are only rats and mice, but there are ing be slow, is probably completed in the Beta range o traditions of dugong as well. Of birds the cardinal, temperature. After a fairly rapid cooling from 950°C sparrow, and mina have doubtless been introduced ; the 0.21 per cent. carbon steel when quenched at 730°C nuddies, frigates, and terns were breeding in enormous micrographically registered a segregation of ferrite so far numbers on certain islands, though it was mid-winter; advanced as strongly to suggest that such segregation must crab-ployer, curlew, whimbal, and a sandpiper were have begun at Ar 3 and not at Ar 2. In other wores common, and in the north-west monsoon buzzards, kites, hardenite is insoluble in ferrite in both the Beta and Alpha and crows are said to be regular visitants. The green ranges of temperature. It however still retains its identity and shell turtles (Chelone mydas and C. imbricata) abound, as hardenite whilst falling through, say, 30° C. or 400 e the former coming on shore to deposit its eggs at night of temperature in the Alpha range, namely, from the e and the latter in the daytime. The only other reptiles of Ar 2 at about 720o C. to the beginning of Ar 1 at about are a marsh tortoise, perhaps introduced from Madagascar, 680° C., at which latter temperature it begins to de and geckoes; there are no Amphibia. There is only one compose into pearlite. The heating transformations of land shell, and arachnids and myriapods are scanty; the this steel are substantially as follows:-At Act (abo land crustacea are similar to those of the Maldives, but ! 710° C.) in the Alpha range the pearlite begins to change the coco crab (Birgus latio) is also abundant. Mr. Bain- into hardenite, hence the carbide is soluble in the

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