276 Mr John Macadam's Analysis of Pottery. 



The surface is also, almost completely covered with marks 

 like scratches crossing each other, forming a kind of net- 

 work which has evidently been done with the hand, aided by 

 some rude instrument. This ornamental appearance resem- 

 bles somewhat in style, that which exists upon the pottery 

 occasionally found in the Druidical tumuli of our own country. 



There are little distinct colourless particles distributed 

 throughout its mass, in size from about 5Vth to ^^^th of an 

 inch in diameter. These, when examined, were found to be 

 pure silica. It would appear, that these had been purposely 

 introduced into the mixture of which the pottery was made, 

 and that they were obtained by the pulverization of quartz, 

 or some other natural variety of silica. 



Organic matter is present to a considerable extent, and, 

 from its general diffusion throughout the mass, would seem 

 to have been added in order to increase the adhesiveness of 

 its particles. In the Babylonian and Egyptian sun-burnt 

 pottery, straw was employed for this purpose. The organic 

 matter present in the American earthenware, however, dif- 

 fers from that present in the ancient Asiatic and African 

 bricks, by its being delicately fibrous, though, like the orga- 

 nic matter present in the Babylonian and Egyptian varieties, 

 it is of vegetable origin. 



A portion of the pottery was submitted to qualitative che- 

 mical analysis. Its constituents were — 



Water. 



Organic Matter. 

 Oxides of Iron. 

 Alumina. 

 Lime. 



With traces of Potash and Soda. 



The respective quantities of these ingredients were then de- 

 termined in the usual manner, viz. : — 



A portion of the powdered material was fused with an al- 

 kaline carbonate. The silica was separated from the fused 

 mass by the addition of hydrochloric acid. From the acid 

 solution containing the soluble matters, the sesquioxide of 

 iron and alumina were jointly precipitated by ammonia. The 

 alumina was removed from the sesquioxide by boiling in pot- 



