COMPOSITION OF BRICK AND MORTAR IN THE GREAT WALL 



OF CHINA • 



By J. C. Witt 



(From the Laboratory of General, Inorganic, and Physical Chemistry, 



Bureau of Science, Manila) 



ONE PLATE 



During a recent trip to northern China I visited the Great 

 Wall at Shanhaikwan. At this point the wall is largely com- 

 posed of gray brick laid with lime mortar. The bricks have a 

 porous structure, somewhat resembling pumice, and are much 

 larger than ordinary building bricks. They are so weak that 

 pieces may be easily broken off with the fingers. The mortar 

 is pure white, under the exposed surface, and is much stronger 

 than the brick. 



The materials were of special interest to me because of recent 

 research in ceramics and lime-burning at the Bureau of Science. 

 A sample of each was taken and analyzed in this laboratory. 

 The construction of the wall began in the third century before 

 Christ, but was repaired eighteen centuries later. Therefore 

 there was no means of knowing the age of the materials sampled, 

 but apparently they were a part of the original structure. The 

 general condition of the wall at this point is very good, as can 

 be seen from Plate I, though near the top a number of the bricks 

 are missing. Table I shows the analytical results. 

 Table I. — Analysis of brick and mortar." 



Determination. 



Brick. 



Mortar. 





P.ct. 

 0.10 

 73.02 

 18.96 



P.ct. 



43.88 

 2.12 

 0.44 



48.83 

 4.03 

 0.85 











1.05 

 5.73 







3 Analyzed by F. D. Reyes, inorganic chemist, Bureau of Science. 



The brick is said to have been dried in the sun only. This 

 was confirmed in the laboratory tests, because on ignition the 

 material becomes dark red. If it had been originally burned 

 in a kiln, the appearance of the wall would have been consid- 

 erably different, and the strength and durability would doubt- 

 less have been much greater. Both the general appearance and 

 the analysis of the mortar indicate that no sand was mixed 

 with the lime. It is apparent also that the stone from which 

 the lime was made was of good quality. 



Received for publication May 16, 1917. 



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