Platinum and the Greenwich System of Time-Signals in Britain THE WORK OF GEORGE BIDDELL AIRY AND CHARLES VINCENT WALKER FROM 1849 TO 1870 By John A. Chaldecott The Science Museum, London The establishment of regular time-signals and their distribution throughout Britain by means of galvanic telegraphy was largely the out- come of collaboration between G. B. Airy and C. V. Walker, with some assistance from the brothers E. and L. Clark. The early history of this development, and the role which platinum occupied in its successful operation, is traced largely from records preserved in the archives of the Royal Greenwich Observatory at Herstmonceux Castle. A broad historical survey of Greenwich time preference was given almost entirely to bat- is to be found in a recent book by Howse (I), teries having metallic platinum present in one and for anyone having a particular interest in form or another. the introduction and development of the Green- The service whereby time-signals were made wich time-signal service from a horological available throughout the country by way of the standpoint there are excellent accounts sup- electric telegraph came about mainly through plied more than a century ago by Ellis (2), who the efforts of two men: George Biddell Airy was then employed as an Assistant at the Royal who in 1835 was appointed Astronomer Royal Observatory, Greenwich, and had day-to-day (9,and Charles Vincent Walker who ten years responsibility for overseeing the time-signal later became Telegraph Superintendent to the service. South Eastern Railway Company (6). The service only became feasible following Ary had no practical experience in galvanic the extensive development of the electric telegraphy (7) but he recognised that possible telegraph, the current for which came from advantages might accrue from the introduction numbers of galvanic cells connected together in of galvanic systems in the Royal Observatory. series to form batteries. In one respect Ellis’s As a starting point he wondered whether with account was not explicit about the type of bat- the assistance of a galvanic battery it would be tery used at Greenwich, for he referred only to possible to make the going of two or more a battery consisting of cells in which the two clocks at the Observatory depend on that of the poles were of copper and zinc, and we know transit-clock. With this in mind he consulted an that several types of copper-zinc cells existed at eminent London chronometer maker, Edward that period, some of which were certainly John Dent, mentioning that ideally the galvanic employed for telegraphic purposes (3). battery should not require frequent renewal but A recent study of documents preserved in the be competent to operate for at least a week and archives of the Royal Greenwich Observatory if possible a month (8). Dent replied that there (4) has served to clarify the position however, would be no difficulty in putting Airy’s pro- and it can now be said that from the start of the position into effect, but mentioned that in trials service a variety of galvanic batteries were in made at an earlier date he had encountered dif- use at Greenwich, though within a few years ficulty from oxidation of the metallic surfaces Platinum Metals Rev., 1986, 30, (l), 29-37 29 George Biddell Airy 180 1 - 1892 A distinguished mathematician, author and ad- ministrator, Airy was often called upon by Government for advice on scientific matters dur- ing the forty-six years that he was Astronomer Royal. One of many honours bestowed on him was the Honorary Freedom of the City of London in recognition of his eminent services which had “so materially benefited the cause of commerce and civilisation” allowed to transmit his time-signals along the railway’s telegraph lines to London Bridge Sta- tion. From there the time-signals might be distributed to stations already on the SER’s telegraph system, and also perhaps to the English Telegraph Company (ETC) whose cen- where the electrical circuit was made and tral telegraph station was situated at Founder’s broken. His own experience had revealed that Court, Lothbury, in the City of London. That by using a battery of Smee cells and having being so, distribution throughout the country platinum and pure gold as the metals where could then be made over the telegraph network electrical contact was made and broken, such a operated commercially by the ETC, to serve battery would last for months (9). other railway companies, and any public in- stitutions or private firms who might wish to Airy’s Plan display Greenwich time. Having received that assurance as regards the An approach was made to Walker in 1849 in- existence of a suitable galvanic battery, Airy forming him of Airy’s wish to have a telegraph realised that it should be possible to send elec- line laid down from the Observatory to trical impulses every second to control the Lewisham Station (I I). Walker responded at movement of “sympathetic” (or slave) clocks once, promising his cordial co-operation; and situated outside the Observatory; and if he after consulting with the Directors of the SER could have a telegraph line connected from the he was able to inform Airy that in giving their Observatory to one of the existing telegraph assent to his plan they regretted that it would systems, he could also make his galvanic time- not be possible for them to bear the cost of in- signals available at designated hours stalling the proposed telegraph line (12). throughout a large area of the country (10). Financial constraints probably precluded His opportunity came when he heard that the Airy from taking any immediate action to im- South Eastern Railway Company proposed to plement his plan and it was not until the year install a telegraph line that would pass within 1851 that he felt able to proceed. His first act nine furlongs (approx. 1.8 km) of the Obser- was to go with Walker to look at some examples vatory. He realised that if he could get permis- of sympathetic clock systems already operating sion for a telegraph connection to be made from in London, all of which were the work of the Observatory to one of the stations on the Charles Shepherd, a well-known London South Eastern Railway (SER), he might be clockmaker. He also went to see the clock Platinum Metals Rev., 1986, 30, (1) 30 Charles Vincent Walker 1812-1882 Inventor, author, editor, and translator of works on electricity and its applications, Walker took an active part in the newly formed London Elec- trical Society. He has been described as the “father” of the profession of electrical engineers, and for thirty-seven years he served as Engineer and Telegraph Superintendent to the South Eastern Railway, in which capacity he assisted Airy greatly in the establishment of the Greenwich system of time-signals system which had been installed by Shepherd at the Great Exhibition building in Hyde Park, being accompanied on that occasion by Shepherd’s son (13). Airy then consulted Shepherd and asked him to provide an estimate of the cost of a sympathetic clock system for the Observatory, including some arrangement for operate continuously. The Smee cell was in- operating the Greenwich Time-Ball electrically, troduced in 1840 by Alfred Smee and im- and also whatever batteries would be required mediately became available commercially (I7). to operate the entire system (14). It was of the single-fluid type, the electrolyte The SER was informed that Au-y now wished being sulphuric acid diluted in the proportion to have six or more telegraph lines installed of one part acid to seven parts water. A sheet of from the Observatory to Lewisham Station, pure rolled zinc, well amalgamated, formed the some to go through to London and others to negative plate, and the positive plate could be provide a means of communication between the platinum, palladium, or pure silver. Before use Royal Observatory and the principal European the positive plate had to undergo special treat- Observatories, once the submarine line from ment, the surface being first roughened all over England to France was completed (I 5). A draft and then platinised by electrolysis for a short agreement was submitted to Ary by the SER, time to acquire a thin coating of platinum and he then wrote to the Board of Admiralty black. Sandpaper was used to roughen plates of setting out his reasons for wishing to proceed platinum or palladium, but in the case of silver (16). The Board’s approval was given shortly the surface was etched with strong nitric acid afterwards and Airy immediately instructed and then washed clean with water (18). The Shepherd to start work on the clock system, function of this platinising treatment was to and Walker was requested to have the installa- promote the easy disengagement of hydrogen tion of the telegraph lines put in hand. bubbles which Smee had observed always tend- ed to adhere more readily to a smooth surface Clock and Telegraph Batteries than they did to one that was irregular; it had The Smee battery, in the form of one or more the desired effect of considerably reducing cells, was the one generally favoured for polarisation when the cell was in operation, and operating electric clocks, as it required little thereby increased its efficiency. The e.m.f. of maintenance and was capable of producing a the cell was about I. I volts (IS), and its internal strong current provided it was not required to resistance around one ohm. Platinum Metals Rev., 1986, 30, (1) 31 usually referred to as “sand-batteries”.