THE WELDON EANGE-EINDEE. 
43 
F to C, lie will arrive at a point, B, where lie will see A reflected on C. 
ABC will then be an isosceles triangle having the angles ABC, ACB 
each = 88° 34' 3", and 20 times the base, BC will equal AB or AC. 
Or suppose there is only one instrument forthcoming; then the 
observer, by using two pickets, can obtain the same result thus :—• 
Planting a picket, D (Fig. 3), at random, he moves until he finds at 
Fig. 3. 
C a place where A is reflected along the line CDF, and here he again 
plants a picket. Moving along the line CF, he arrives at a spot, B, 
where A is reflected on the line of the pickets D and C. As before, 
20 times BC = AB or AC. 
After some years spent in attempts to obtain the satisfactory reflec¬ 
tion of an angle of 88° 34' 3", Major Weldon has now introduced an 
instrument so simple that until used it is difficult to believe that with 
such an apparent toy, distances varying from a few yards to many 
thousands of yards can be accurately measured. Its cost, at present, 
is about 30 shillings. It is little larger than a walnut, weighs but a 
few ounces, and can be carried in a small pocket. It requires no 
adjustment, and will stand rough usage. 
Fig. 4. 
(Eeal size.) 
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