^52 Extracts from Dr Hibbert’s Description 
therefore, in a boat, a narrow channel, little more than half a 
mile in breadth, we are landed immediately under its walls. 
The Burgh of Mousa occupies a circular site of ground, 
somewhat more than fifty feet in diameter, being constructed of 
middle sized schistose stones of tolerable uniform magnitude, 
well laid together, without the intervention of any cement* 
This very simple round edifice attains the elevation of 4J2 feet ; 
it swells out^ or bulges from its foundation, and draws smaller 
as it approaches the top, when it is again cast out from its lesser 
diameter; which singularity of construction is intended to ol>- 
viate the possibility of scaling the walls. The door that leads 
to the open area contained within the structure, is a small nar- 
row passage, so low that an entrance is only to be accomplished 
by crawling upon the hands and knees ; and in creeping through 
it, the wall appears of the great thickness of 15 feet, naturally 
leading to the suspicion of a vacuity within. On arriving at 
the open circular area included within this mural shell, I found 
the diameter of the space to be about 21 feet. On that part of 
the wall within the court, which is nearly opposite to the en- 
trance, the attention is excited by a number of small apertures 
resembling the holes of a pigeon-house. There are three or 
four vertical rows of them, having each an unequal proportion 
of openings, varying from eight to eighteen in number. It was 
now evident that the mural shell of the structure was hollow, 
and that it contained chambers, to which these holes imparted a 
feeble supply of light and air. Beneath the whole, at a little 
distance from the ground, there is a door that leads to a wind- 
ing flight of stone steps, of the width of 3 feet, which commu- 
nicates with all these apartments ; I then discovered that the 
shell of the Burgh was composed of two concentric walls, each 
of about 4 1 to 5 feet in breadth, and that a space of nearly a 
similar dimension was devoted to the construction of the inner 
apartments. In ascending these steps, which wound gradually 
to the top of the wall, I observed that they communicated at 
regular intervals with many chambers or galleries, one above 
another, that went round the building. These were severally 
of such a height, that it was possible to walk within tlieni nearly 
upright. The roof of the lowest chamber was the floor of the 
second, and after this manner seven tiers were raised. On 
