Instrument	:	Cross-staff, baculus Jacob, Jacob's staff, ballastella, arbalestrille, fore-staff, graadstok, graadboog,...
Manufacturer	:	N. de Hilster (original by J. Hasebroek).
Country of origin	:	The Netherlands (Original also)
Manufacturing year	:	2004 (Original: 1720)

After finishing the back-staff replica I wanted to reconstruct an even older navigational instrument: the Cross-staff. I decided to go for a replica of the 1720 Jochem Hasebroek Cross-staff as its dimensions where not too large, so getting the correct wood in it's right dimensions should not pose any problems. Another reason to go for a late cross-staff was that I wanted to create a staff with all the possible 'options' available (4 vanes, altitude and zenith graduation and the Dutch shoe, although the latter was not found with the instrument).

I started working on this staff in January 2004 and finished it by the end of March.

The first description of the baculus Jacob dates back to 1342 (Levi ben Gerson [1288-1344]) and it was introduced at sea by the Portuguese around 1515. This instrument was the forerunner of many different staffs of which the Davis Quadrant is the most famous. In the beginning the cross-staff was used facing the sun and therefor required the navigator to look straight into the bright sunlight. With the invention of the Davis Quadrant one could simply measure facing away from the sun, a big advantage over the cross-staff. For this reason the Davis Quadrant was also referred to as the back-staff, while the cross-staff was also referred to as the fore-staff. After the introduction of the back-staff the cross-staff was also used in a backwards fashion, casting the shadow of one of the vanes on a bone that was attached to the smallest vane. In the middle of the 17th century the Dutch invented the Dutch shoe, a clamp that fitted to the end of the larger vane improving the quality of the backwards observation dearly. Both the cross-staff and the back-staff were used until the introduction of the octant^*).

Materials used on this reproduction are ebony for the staff and pear wood for the vanes.

I'm very grateful to Klaus Staubermann (former curator of the University Museum of Utrecht), Diederick Wildeman and Willem Mörzer Bruyns (both Scheepvaartmuseum Amsterdam) as without their help and information (I was even allowed to study several original instruments) the detailed reproduction of this instrument would never have been possible. I also wish to thank Peter Ifland for introducing me to Klaus Staubermann.

Want to know if your staff belongs to a spiegelboog or cross-staff (and if it is a cross-staff you can check if the vanes are right)? You can check it yourself here.

^*)The Cross-staff, History and Development of a Navigational Instrument by W.F.J. Mörzer Bruyns, 1994.

If you like to know more, don't hesitate to contact me.