b Engraved
A chart watermarked 1825 has been found with the price engraved below the seal, whereas, as stated above, a chart watermarked 1826 without the engraved price has also been seen.

c Price Changes
The prices of charts were altered from time to time. Initially, the change was made in red ink until the price could be re-engraved. Changes in the price of one particular sheet were noted from the Admiralty chart catalogues as follows: first priced in 1825, altered in 1826, 1830 and 1846, and then unchanged until 1856 when the chart was withdrawn. An odd variation noted was the amendment, on the chart itself, of a price of 'Six p.' to 'Sixpence,' with a similar alteration for a price of one shilling. Possibly there was a further change between these two pairs of prices. Used in conjunction with the published chart catalogues, these price changes can help to pinpoint the actual date of a particular chart. Since the ink price would have been added to a chart which had possibly been printed some time before, it would, however, indicate the date of issue, not the date of printing.

Successive forms of the Hydrographic Office Seal:


5 Chart numbers
Chart numbers were first allocated in the 1839 chart catalogue. Charts with and without engraved numbers have been noted on paper watermarked 1839. An instance has been encountered of a chart number added in ink. Since this probably represents a post-1839 addition to an already printed chart, it, again, would indicate the date of issue, not of printing. When the numbers were first allocated, they followed the geographical sequence of the existing catalogue. Thus numbers 7-24 were given to the south coat of England, 242-252 to the north coast of Africa, and so on up to 1116. However, as no gaps were left, numbers above 1116 were allocated thereafter in the order of publication and have no geographical significance. 1154, for example, also belongs to southern England. Confusingly, the numbers of withdrawn charts were sometimes re-allocated to those covering entirely different areas and sometimes applied to later charts of the same area. In several cases, however, the charts have been cropped so closely that the chart number (placed outside the outer rule) has been cut off.


6 Admiralty agents

a Bate
Between 1821 and 1829a number of chartsellers shared the agency for the sale of Admiralty charts. On 25 September 1829, R. B. Bate was appointed sole Agent. A statement that the chart in question was sold by Bate was inserted by hand-stamp below the publishing imprint. This has been seen on a chart watermarked 1833, but it probably occurred earlier. Later, this statement was engraved directly onto the charts, probably after 1840. Not all charts carried Bate's imprint. On the death of her husband in December 1847, the Admiralty allowed Mrs Bate to continue the agency in her husbands name, though with some misgivings. No changes to the charts resulted from this.

b Potter
J. D. Potter, who had been Bate's foreman for some years, was appointed Chart Agent on 20 April 1850 on Mrs Bate's recommendation. Potter's imprint was inserted in place of Bate's, probably soon after his appointment (though Bate's engraved imprint has been seen on a chart issued in March 1851). The firm of Potter continued to hold the agency into the present century.

7 Changes of the late 1850s
In 1855, the printing of Admiralty charts was entrusted for the first time to an outside firm, Malby Brothers. The following changes, which seem to date from the same period, may be connected with that development.

a Paper
An opaque, unwatermarked, machine-made paper replaced the fine-quality wove sheets used earlier. However, a watermark date of 1862 has been seen.

b Stippling
Day (p.50) records that 'in 1851, on a proposal of a Mr B. G. Sloper, Beaufort decided to apply a land-tint to some general charts only, while showing anxiety that the coastline detail would be obscured.' The result was a stippled grey pattern, added uniformly over the land areas except where coastal relief would have been smothered. This pattern was inserted equally on new charts and on amended forms of existing ones. Although used for shoals on one 1854 chart, its inland application was first detected by Day on a chart of 1855.

c Lighthouses
These were emphasized by means of a yellow aureole with an orange centre, applied by hand. This feature was absent from two 1853 charts but present on one of 1854. This is not necessarily a reliable dating guide.

d Lithography
Although experiments with lithography, a far quicker process than copper engraving, were made from at least 1827, and an example dating from 1854 has been noted, lithographed sheets, signed by Malby Bros, appear with more regularity from 1856 onwards. Their use tended to be restricted to temporary or less important work.

8 Corrections
It is always worth checking the content of a chart, since added hydrographical information was sometimes inserted or the magnetic variation updated without any alteration to the imprint.

9 The dating features summarized
When looking at a particular early chart it is wise first to check the watermark (see note 2) and then the following points, since these can indicate a later date than that given in the imprint:

1804 Hydrographical Office hand-stamp (3a)

c. 1810 Engraved Hydrographical Office seal (3b)

1822 Prices added in red ink (4a)

c. 1826 Prices engraved (4b)

1829 Bate agency (6a)

1839 Chart numbers added (5)

1850 Potter agency (6b)

c. 1855 Machine-made paper and land stippling (7a, 7b)

NB Alterations which did not affect the engraved copper plate – e.g. information inserted by hand-stamp or in ink – could have been added to a particular impression some time after it was printed. Hand-applied elements could also be omitted. Engraved alterations, on the other hand, affected immediately every impression taken from the copper plate concerned.