HABITATIONS OF INSECTS. 511 



or oval galleries of different diameters. The necessity for 

 the vast size of the main underground galleries evidently 

 arises from the circumstance of their being the great 

 thoroughfares for the inhabitants, by which they fetch 

 their clay, wood, water, or provision ; and their spiral 

 and gradual ascent is requisite for the easy access of the 

 Termites, which cannot but with great difficulty ascend 

 a perpendicular. To avoid this inconvenience, in the 

 interior vertical parts of the building, a flat path-way, 

 half an inch wide, is often made to wind gradually, like 

 a road cut out of the side of a mountain, by which they 

 travel with great facility up ascents otherwise impracti 1 

 cable. The same ingenious propensity to shorten their 

 labour seems to have given birth to a contrivance still 

 more extraordinary. This is a kind of bridge oT one ' 

 vast arch, sprung from the floor of the area to the upper 

 apartments at the side of the building, which answers 

 the purpose of a flight of stairs, and must shorten the 

 distance exceedingly in transporting eggs from the royal 

 chambers to the upper nurseries, which in some hills 

 would be four or five feet in the straightest line, and 

 much more if carried through all the winding passages 

 which lead through the inner chambers and apartments. 

 Mr. Smeathman measured one of these bridges, which 

 was half an inch broad, a quarter of an inch thick, and 

 ten inches long, making the side of an elliptic arch of 

 proportionable size, so that it is wonderful it did not fall 

 over or break by its own weight before they got it joined 

 to the side of the column above. It was strengthened 

 by a small arch at the bottom, and had a hollow or 

 groove all the length of the upper surface, either made 

 purposely for the greater safety of the passengers, or else 



