no 



NA TURE 



[June I, 1876 



Thanks to the generosity of the Pacific Mail Steamship 

 Company in passing the baggage free, Mr. Agassiz and 

 his companion took to Peru a large outfit in the way of 

 ropes, dredges, sounding-leads, thermometers for deep- 

 water temperatures, and all the necessary materials for 

 preserving large collections. 



Though they were greatly disappointed in the variety of 

 animal life found in the lake of Titicaca and the surround- 

 ing shore, they took some very interesting deep-water 

 temperatures (to a depth of 154 fathoms), and completed a 

 preliminary hydrographic sketch of the Lake, which has 

 furnished valuable results, and done much to explain the 

 poverty of its animal hfe. 



The success of the Memorial-fund, of which we have 

 spoken above, will, it is anticipated, enable the principal 

 ideas of the late Professor Agassiz to be accomplished, so 

 soon as the necessary additions to the buildings are 

 completed. 



" The foundation will then be laid of an institution in 

 which the claims of college- students, of teachers, of special 

 students, of advanced workers, and of original investigators 

 will be considered, as far as the means and space of the 

 establishment will allow. The public will find in the ex- 

 hibition-rooms all that is likely to be of interest from the 

 stores of the institution, labelled and arranged so as to be 

 not only instructive, but suggestive. 



" Of course time alone will enable us to fill out and 

 complete this plan. We shall be compelled at first to 

 make a very unequal exhibition, but as the blanks become 

 apparent they will be filled. 



" From our stores necessary materials for the constantly 

 increasing number of students are to be supplied, and one 

 of the chief duties of the Curator must always be to meet 

 the reasonable demands of those charged with the instruc- 

 tion, by supplying them with ample materials suited to the 

 wants of the different classes engaged in study at the 

 Museum. The special students will have at their com- 

 mand, under proper regulations, in the store and work- 

 rooms, of the assistants, the materials of the department 

 in which they are interested. 



" To the original investigator the resources of the 

 Museum will always be available, under generous restric- 

 tions, with facilities for the publication of investigations 

 made with Museum materials, as far as the means of the 

 institution will allow. On the completion of the additions 

 proposed at present, the Museum will thus consist of 

 several departments of natural history, formerly separated 

 in the University, and now all more or less intimately 

 connected." 



In concluding our notice of this report, we shall, we are 

 sure, to be heartily joined by every European naturalist in 

 wishing that these excellent plans of the Director of the 

 Museum of Comparative Zoology may be speedily and 

 efficiently carried out. 



THE GREENWICH TIME SIGNAL SYSTEM^ 



II. 



VWE have now to speak of the use made of the time 

 ^ * signals beyond the Observatory walls, and will first 

 refer to the hourly currents passing to the Post Office. The 

 original time-distributing apparatus was comparatively 

 simple ; afterwards Mr. C. F. Varley devised the chrono- 

 pher, an elaborate system of switches and relays provided 

 with an accurate clock for opening and closing the 

 switches at the proper times, and forming together a 

 complete automatic system ; but on the transfer of the 

 central telegraph station from Telegraph Street to the new 

 building in St. Martin's-le- Grand, it was found necessary 

 to add a second and much larger chronopher, shown in the 

 accompanying drawing. It is to this apparatus that the 

 Greenwich wire is led, and by which the single Greenwich 



' Continued from p. 52. 



current is simultaneously retransmitted on many different 

 lines. These lines may be considered as divided into 

 four groups : — i, the metropolitan ; 2, the short provin- 

 cial ; 3, the medium provincial ; and 4, the long provin- 

 cial. The first group consists of wires passing to points 

 in London ; the second of wires passing to towns within 

 a moderate distance of London, as Brighton, &c. ; the 

 third of wires passing to greater distances, as Hull, &c. ; 

 and the fourth of wires passing to towns or places at a 

 considerable distance, as Belfast,^ Edinburgh, Guernsey, 

 &c. In each of the four groups the London ends of the 

 several lines are brought into direct connection, each 

 group having its separate battery and relay. On these 

 four relays (the two at the left hand and two in the centre 

 of the six shown) the current from Greenwich acts, and 

 in each relay circuit the local battery current so divides 

 that a portion of it passes out on every wire of the group. 



The distribution in London takes place every hour ; 

 these wires, being used for time-signal purposes only, 

 remain always connected to the metropolitan relay. To 

 the country, distribution is made twice only on each day, 

 at loh. A.M. (by the new chronopher), and at ih. p.m. (by the 

 old chronopher), using the wires of the ordinary telegra- 

 phic service, which have, in consequence, to be specially 

 switched into connection with the chronopher. The 

 action at both hours is similar ; we shall therefore de- 

 scribe only the loh. A.M. distribution, which is the more 

 extensive. Shortly before loh. the chronopher clock (not 

 shown in the sketch) sets in motion the clockwork train 

 shown in the centre of the drawing ; this turns over on 

 its axis the flat bar (extending from side to side across 

 the row of upright springs), which pushes the springs 

 backwards, each one out of contact with its corre- 

 sponding little square stud above. Each spring is in 

 connection with a distant town or telegraph station, 

 the corresponding stud communicating with its particular 

 speaking instrument in the London office. As soon, 

 therefore, as the springs are pushed back, the speaking 

 instruments become all cut off, and the springs (repre- 

 senting distant stations) remain in contact with the long 

 bar. This bar consists of three insulated portions, one 

 for each of the three groups of provincial wires, each 

 having its own battery and relay as before mentioned, 

 and when it comes into contact with the springs in the 

 way described, the distant stations all receive a constant 

 current which serves as warning. On arrival of the 

 Greenwich current at the chronopher the relays act and 

 reverse these battery currents, and these reversals of 

 current indicate at the distant stations the hour of loh. A.M. 

 precisely. Shortly after loh. the clock-work train causes 

 the long bar to turn back into its ordinary position, the 

 springs become restored each to its respective stud, 

 bringing the lines all into communication with their 

 several speaking instruments, and the ordinary tele- 

 graphic work goes on as before. Of two relays on the 

 right in the drawing, one (by action from the chronopher 

 clock) opens out the relay coils a few seconds only before 

 the hour, and so prevents interruption from accidental 

 currents in the Greenwich line ; the other is concerned in 

 the Westminster clock signalling, spoken of further on. 

 The galvanometers are for showing the passage of the 

 various currents of which we have been speaking. 



In some cases the current drops a time-ball on the roof 

 of a building, in others a model time-ball is exposed to view 

 in some place accessible to the public ; sometimes the 

 current acts on an electric bell, or ordinary galvanometer, 

 and in some cases a gun is fired. The last-mentioned 

 manner of communicating time to the public is one of the 

 most generally useful for ordinary purposes, provided that 

 the observer makes allowance for the rate at which sound 



^ It is to be remarked that although the signals pass into Ireland, Green- 

 wich time is counted only in Great Britain, Dublin time being counted 

 throughout Ireland. In regulating clocks in Ireland by the Greenwich 

 signals, allowance has therefore to be made for the constant difference 

 between Greenwich time and Dublin time. 



