478 On AN INDIAN METHOD oF 
D D_.. forced into:the grooves, extending across the chasm. From 
these as from a new base, the grooved stones alreatly described 
Fig. 2 F F were used. The length of each succeeding layer contracting 
Fig. 3 EK gradually, until the application of the key stones. 
Wuen the arch is of considerable span, a series of bases 
such as now described, is placed, each base higher than the 
Fig. 2 other, in order to support the work until it is secured by being 
lH keyed. 
Fig. 2 Wuen the center portion of the arch has -been thus com- 
FF pleted, the beams are removed, by being sawed asunder in two 
places. 
Iy a similar manner the arch was continued in different 
FG portions at either end of that part first finished. The introdue- 
H tion of a new beam constituting with it, a renewed base. A 
slight scaffolding supported the workmen. | 
In this simple, though ingenious manner, was an arch 
across a space of twenty-two feet, erected, without ‘any frame 
_ for its support while building. 
Tre principle seems applicable either in masorry or cast 
iron, to an arch of any dimensions. 
