|The best existing reference for the pilot guides and Sea Atlases of
Jacob Aertsz. Colom is the fourth volume of Atlantes Neerlandici by Dr.
Ir. C. Koeman, published in Amsterdam in 1970. However, at the time
of publication, he noted that: "The bibliographical treatment is quite
incomplete due to the lack of material". The following collations of two
Atlases in the British Library and two more in private collections may
begin to help in filling in some of the gaps.
||Number engraved on plate, if any.
||Position of the chart in the Atlas.
||Appearance of the same, or similar, chart in other Colom Atlases listed
||Height vs. width, within ½ cm. As insets are mostly
irregular, their measurements are frequently preceded by a
circa, or c. Note that the measurements given for same chart included
in two different Atlases can vary due to shrinkage or stretching caused
by differences in humidity and temperature during storage and as a result
||Colom included a scale bar in the majority of his charts, showing Duytsche
mylen, Spaensche mylen and Engelse en Franse mylen. 15
German, 17.5 Spanish or 20 English or French miles corresponding,
in turn, to 1º of latitude as measured along the
equator. All measurements were made using the Duytsche mylen bar.
In converting, I have used the figure mentioned in Doursther, H.
Dictionnaire Universel des Poids et Mesures, republished by Meridian, Amsterdam,
1965. Doursther states the German Meile as being 7.4089 km., so 15
German miles would represent 111,133.5 mts. or 1º.
I have chosen to show the resulting scale for each
chart, though these numbers should be taken as approximate due to the limitations
involved in precise measurement and the changes
undergone by the paper over three and a half centuries as mentioned above.