THE ROYAL ARTILLERY INSTITUTION. 
50 ? 
A few remarks on Hill Sketching. 
By the aid of a pocket compass and a scale of shade protractor, a tolerably 
accurate field sketch may be plotted on paper; the former instrument will 
enable the sketcher to fix the positions of the different objects in plan, and by 
means of the latter and a small plummet line the contours of the ground may 
be found, and the different inclinations then shaded as per scale of shade. 
The boxwood protractor has a scale of 33rds of an inch marked on the 
bevelled edge. Assuming 32 inches as the average pace of an individual, one 
mile will be equal to 1980 paces; so that, if required to make a military 
sketch on a scale of 6 inches to the mile, ^rd of an inch would represent 
10 paces— 
If on a scale of 12 inches to the mile, ^rd — 5 paces. 
. 24 „ „ „ 2J * 
« 30 „ „ „ 2 . 
n 60 « u n. 1 k 
In field sketching, the unit of measurement must be the pace; and this of 
course is a variable quantity, dependent upon the length of the individual's 
stride. If the sketcher's pace is wide of the 32 inches, a comparative scale 
may be shewn on his sketch afterwards; but it must be remembered that a 
military sketch does not pretend to very great accuracy, so that if his pace 
is within 2 inches of the assumed length of a pace, he may ignore the 
discrepancy. 
The protractor can be used as a levelling instrument, and the contours of 
a hill sketched in, in the field. 
If a line about 6 inches in length, with a bullet attached to one end, and 
the other end of the line run through a hole in the protractor a little above 
the point numbered 9 on the scale of 33rds, and the protractor held in such 
a position that this plummet line coincides with the line joining the 9 and 
the 90°, by looking along the edge of the protractor we shall obtain a 
horizontal line. (Yide Big. 4.) A series of contours can then be plotted with 
Eig. 4. 
a vertical interval of the height of the sketcher's eye from the ground, the 
directions of the different watercourses having been laid down on paper. The 
sketcher can commence at the lowest point, and run a number of cross- 
sections over the ground. By joining the points of the same level, he will 
have obtained a plan of the contours. A cross-section can be run in the fol¬ 
lowing manner:—Let ABC be the section of a hill. The sketcher, standing 
at a point A } and levelling up the incline, observes that point 5 is of the 
