108 MAPS AND THEIR MAKERS 



details of his observations in his notebooks, and then drawn 

 out his map from them in the winter months, though others 

 may have plotted the rays in the field. The former method 

 had obvious drawbacks, and made it easy for errors to creep 

 in. About this time, however, an advance was made which 

 enabled the surveyor to draw his map as he went along. Instead 

 of using the sighting rule mounted on the horizontal circle, 

 divided in degrees, the surveyor placed the sighting rule 

 directly on his drawing paper, mounted on a table, and align- 

 ing it on the distant object, ruled in his ray directly: provided he 

 was careful to orient his table correctly at the successive 

 stations, he could obtain as accurate results as with the hori- 

 zontal circle. This method was referred to by Leonard Digges 

 when he wrote his Tantometria', 1571: 



"Instead of the horizontal circle, use only a plaine table 

 or boarde whereon a large sheet of parchment or paper 

 may be fastened. And thereupon in a faire day to strike out 

 all the angles of position each as they find them in the field 

 without making computation of the Grades and Scruples" 

 (i.e. without observing directly the degrees and fractions). 



This, as Digges* phrase in fact suggests, was the origin of the 

 plane table, which was later greatly developed for filling in 

 detail around the fixed points. When the technique was fully 

 evolved, the plane table virtually became a survey instrument. 

 Some time before 1570, William Bourne was using these 

 methods around Gravesend and Tilbury.^ 



The well-known extract from the Privy Council warrant 

 issued to Christopher Saxton when he was embarking on his 

 surveys of the English and Welsh counties suggests that his 

 methods had some resemblance to those of Apian: he was to be 

 "conducted unto any towre, castle, high place or hill to view 

 the country . . . accompanied with two or three honest men 

 such as do best know the country for the better accomplish- 



^Taylor, E. G. R., William Bourne; a chapter in Tudor geography. 

 (Geogr. Journ., 72, 1928, 335.) 



