ON USEFUL AND ORNAMENTAL STONES OF ANCIENT EGYPT. 3 



gneiss. Though the minerals in these two kinds of rock may 

 be the same, they are distinct both in macroscopic and micro- 

 scopic characters and mode of occurrence, and should not be 

 confounded by geologists. Though the granites may in 

 some cases be locally impressed with a laminated texture, 

 there is no necessity for confounding them with gneisses, 

 which are true bedded rocks ; and their practical value, as 

 well as the natural products derivable from the two classes 

 of rocks (as soils and sands, for instance), are quite different. 

 Huge dykes of the intrusive granite occur at Assouan, 

 traversing the gneissic beds, and thick beds of the gneiss, 

 interstratified with micaceous arid hornbleridic schists. Both 

 .species were worked by the ancient Egyptians. The great 

 obelisks and the lining stones of the Temple of Bubastis, 

 or some of them, are examples of the former. The 

 broken colossus of Rameses at the Ramesseum, in Thebes, 

 is a good example of the latter. The stupendous fragments 

 of this statue confirm the description of Diodorus, who 

 commends it not only for its great size, but for the " excel- 

 lence of the stone." This is, in fact, not a granite, but a 

 mass taken from a thick bed of gneiss of fine colour and 

 uniform texture, and more dense and imperishable than any 

 true granite. It must have sat 60 feet high, and before it was 

 sculptured must have weighed about 900 tons. It was sur- 

 passed by but one other statue in Egypt, that gigantic one 

 discovered by Petrie at Tanis, known only in fragments, 

 which seems, without its pedestal, to have been at least 80 

 feet in height. It also was of the red stone of Syene. Of 

 the two lands of so-called Syene granite, the gneissic 

 variety is the more compact and durable, and the more re- 

 sisting to the action of the weather. This is a usual circum- 

 stance elsewhere, and probably depends on the fact that the 

 gneisses have been subjected to extreme pressure during 

 their crystallisation. The orthoclase gneisses and granites 

 of Assouan are not distinguishable from those of the Lau- 

 rentian series of North America. The gneissic variety used 

 in some of the older structures at Gizeh is porphyritic, or an 

 " augen-gneiss," having large crystals of pale-reddish 

 felspar. 



The shallower sculptures on many monuments of this 

 stone seemed to have been chiselled'in the usual way, but 

 the more deeply-cut hieroglyphics and figures were probably 

 worked in the first instance with the hollow drill. 



A very remarkable stone employed in Egyptian sculpture 

 is that variety of gneissoid rock known to Canadian geolo- 



102 



