Go back to article: Visualising electricity demand: use and users of a 3D chart from the 1950s

A close inspection of the object

Figure 3

Colour photograph of a 1950s three dimensional chart showing electricity demand over time

Metal rails anchor the cards in position

The chart is comprised of 675 cards held in place by two metal rails running the full length of the object, with steel uprights in each corner of the wooden base (see Figure 3). It is quite large – 67 x 31 x 36cm – about the size of a desktop printer, and heavy, but it has a handle at each end to make it portable. It was formerly glazed, and the broken fragments of glass are still stored with the object. Four green felt pads on the underside of the object suggest it was treated as a decorative object, and possibly placed on valuable wooden furniture (see Figure 4).

Figure 4

Colour photograph of the wooden underside of a 1950s three dimensional chart showing electricity demand over time

Green felt pads on the underside of the object have worn away over time

Each card shows the demand for electricity in megawatts (MW) for each half-hour period over 24 hours, from 2 October 1951 to 30 April 1954 (see Figure 5). Despite the accompanying key showing a seven-day week, there are only cards for Monday to Friday, mass printed in the five colours, and then annotated with a date stamp and a handwritten prefix for the day of the week.

Figure 5

Colour photograph of two individual chart cards from a 1950s three dimensional chart showing electricity demand over time

Sample of cards showing data recorded, and the key to the colours that enabled viewers to pick out a day of the week at a glance

The time of sunrise and sunset is marked on each card, as is temperature and ‘remarks’ on the weather. These remarks match the daily weather summaries for the past 24 hours for Manchester, published daily in the Manchester Guardian (see Figure 6), and were written onto the cards in more than one pen and handwriting. Rainfall is occasionally noted, but other boxes for ‘Wind, direction’, ‘Wind, force’ and ‘Visibility’ are never completed.

Figure 6

Colour photograph of an individual chart card from a 1950s three dimensional chart showing electricity demand over time alongside a corresponding weather report from a local newspaper

Left: Weather report in The Manchester Guardian on 16 December 1952, with a weather summary for the past 24 hours stating ‘Snow and hail showers followed by bright periods’ (credit: Manchester Guardian); Right: Image of card from 15 December 1952, with a matching weather remark (credit: Museum of Science and Industry)

There are also occasional annotations written onto the graphical section of the card, two of which give clues about the geographic area from which the data was drawn. The two cards shown in Figure 7 refer to ‘Barton’ and ‘generating stations’ in the plural suggesting the area included Barton power station, and at least another. Using data on plant capacity from Swale’s Forerunners of the North Western Electricity Board (Swale, 1963), and the value of the highest peak demand (450 MW on Tuesday 2 December 1952), we surmise that the meter readings were taken from generating stations in the Board’s Sub-Area Number 1 – Manchester, the generating stations that were owned by Manchester Corporation before nationalisation in 1948.

Figure 7

Colour photograph of two individual chart cards from a 1950s three dimensional chart showing electricity demand over time

Top: ‘Faulty readings at Barton, meter unreliable’; Bottom: ‘Heavy rain’, ‘Readings checked O.K. with Generating Stations’. Annotations giving clues to the geographic area from which meter readings were taken

Traces of pencil and red pen ink across the profile of cards suggest that the data values were drawn onto the card before being cut by scissors or a clipper (see Figures 8 and 9). The height of the card from which they were cut is evidenced by an offcut sandwiched in the middle of the model (see Figure 10) – the maximum demand printed on the card is 640 MW.

Figure 8

Colour photograph of two individual chart cards from a 1950s three dimensional chart showing electricity demand over time

Cards showing pencil and red pen ink marking the values onto the card. The red pen ink continues for a sequence of cards

Figure 9

Colour photograph of two individual chart cards from a 1950s three dimensional chart showing electricity demand over time

Scissor marks at the base of the ‘valley’ and paper tags in corners suggest the cards were cut with scissors or clipped

Figure 10

Colour photograph of an individual chart card from a 1950s three dimensional chart showing electricity demand over time

An offcut in which the rail bar has been cut into the upper edge is evidence of what was discarded during the construction of the object

Taken together, evidence from the object led to the following interpretations. The chart was probably assembled day-by-day, or for a group of days, rather than all at once, and the values were cut into the cards by hand – a time consuming task. Daylight hours and weather variables were important enough to record, and the whole chart was probably on display for some period after initial construction. We were not able to find a similar object with which to compare it for Fleming’s (1974) step of ‘evaluation’, but it seemed to have a purpose beyond the recording of daily load curves – a need to see the data in relationship, or trends. An analysis of these trends would also fulfil Fleming’s third step of ‘cultural analysis’: the relationship of the object to its culture.

Component DOI: http://dx.doi.org/10.15180/180905/002