46 The Dalb]i Profile Recorder 



clamped. The profile curve corresponding to each pair of notches 

 provided is then drawn. 



The family of curves, Fig. 1, were drawn in this way. 



4. Interpretation of the Profile Curves on the Record. 



The datum lines lie in one plane, the plane of reference. The distance 

 from any point on any one of the profile curves to its datum line is 

 equal to twice the distance of the corresponding point in the timber 

 surface to the reference plane defined by the point Z. 



For example the point Fj on the Record No. 1 (drawn again in Fig. 6) 

 is I" above the reference plane containing the point Z on the surface of 

 the sample. Similarly the point Y^ is 0-2" below this reference plane. 



All the points on the timber surface corresponding with points of 

 intersection of the profile curves with their respective datum lines lie 

 in the reference plane containing Z. 



For example the points on the surface corresponding to points 

 Zzzzz and yyyyy in the record all lie in the plane of reference. The 

 lines joining these points are contour lines in the reference plane. 



Points on the profile curves at equal distance from their respective 

 datum lines can be located. Curves through these points are contour 

 curves for the particular distance located. 



The family of profile curves drawn by the machine can therefore 

 be used to find the contour lines of the surface explored. And these 

 contour lines can be drawn on the record. 



A family of profile curves of sections at right angles to those drawn 

 automatically by the machine can be deduced. Suppose for example 

 that the profile is required across the section SS on the record shown 

 in Fig. 6. At each of the intersections of SS with the five datum lines 

 of the record, set up (or down) the intercepts on SS, cut of! by the re- 

 spective datum lines and the corresponding profile curves. PiP^P^P^P^ 

 are points obtained in this way and the curve through them is the profile 

 curve across the section SS. 



Profile curves for a series of transverse sections at any assigned 

 interval apart can be deduced from the family of profile curves drawn 

 by the machine. Such a family is shown in Fig. 7 for transverse sections 

 taken about 3" apart on record No. 2, a record taken from an artificially 

 prepared surface of a sample of pine. 



