770 THE POPULAR SCIENCE MONTHLY. 



locality, " A good hat and a good pair of shoes is all that cob 

 wants." The pair of shoes here meant is a stone foundation such 

 as I have described in the Persian houses that is, to protect 

 the lower part of the wall ; and the hat is a sufficient amount 

 of thatch, or covering, to the top of the wall to save it from the 

 influence of rain. With such conditions, I believe that mud walls 

 in Devon, even in our own damp climate, have stood for long 

 periods of time. 



The sloping jambs of doors and windows are peculiar to many 

 old styles of architecture, such as the early Greek and Etruscan. 

 Theories of origin for this have been often suggested, but we have 

 no difficulty in accounting for them, if we suppose that the nar- 

 rowness above was a form, and the natural result of the sloping 

 walls of mud. 



I have already explained how builders in mud and which is 

 well exemplified in Persia construct their walls with a broad 

 base, to give solidity below, and with a marked batter upward to 

 reduce the weight above. It has been suggested and, I think, 

 with every reason in its favor that this explains the very marked 

 slope of the perpendicular lines of the Egyptian pylons. All the 

 authorities agree in stating that in the old temples the outer wall 

 forming the temenos of temples of Egypt was made of crude brick, 

 and as the pylon was the gate through this wall in front of the 

 temple, the great probability of its being constructed of the same 

 material is obvious. 



When I had seen village after village in Persia with vaulted 

 or domed roofs, and learned that such roofs could be formed with- 

 out centers, the idea immediately suggested itself that these 

 methods of building had existed from the most primitive times. 

 While the necessity for wooden centerings for building vaults 

 and domes was believed in, we never could have credited an early 

 state of civilization with this invention. Let this assumption re- 

 garding centers be removed, and the whole problem is changed. 

 The earlier workers in mud or clay could not have been long in 

 discovering how to spread their material over the space inclosed 

 by four walls. They would, no doubt, have begun at first with 

 small spaces, and a very little experience would soon have enabled 

 them to deal with greater. If any one considers the matter, I 

 think he must arrive at the conclusion that mud must have been 

 first used for a long period of time before burned brick came into 

 existence ; and now that we know how easy it is to produce a roof 

 with the mud, there is no great improbability in the assumption 

 that the vault or dome, as well as the arch, all date back to a 

 period when that material alone was in use. 



I have described the foundations of a mud wall, such as they 

 are in Persia, formed of burned bricks or stones and lime ; and also 



