762 THE POPULAR SCIENCE MONTHLY. 



that the absorption of immigrants has not been equal. The facts 

 in this respect can not be given for 1890, but for 1880 they indi- 

 cate what may be expected when the full facts for 1890 are re- 

 ported. In 1880 the whole number of people engaged in agri- 

 culture was 7,070,493. Of this number 812,829 persons were of 

 foreign birth ; that is to say, 10*06 per cent of the whole number 

 employed in agriculture in 18S0 were foreign-born. The total 

 number employed in manufacturing, mechanical, and mining in- 

 dustries in the United States in 1880 was 3,837,112. Of this num- 

 ber 1,225,787 were of foreign birth, and this number is 32 per cent 

 of the whole number of persons engaged in these industries. The 

 tendency, therefore, of our immigrants is to assimilate with our 

 mechanical industries. This increases the supply of labor in 

 comparison to the demand, and may in some localities tend to 

 lower wages, and sometimes to cripple the consuming power of 

 the whole body of the people. In 1880 12'52 per cent of the whole 

 number of foreign-born persons were engaged in agriculture, 

 while 18"88 per cent of the foreign-born were engaged in manu- 

 factures. 



MUD AS A BUILDING MATERIAL. 



Br WILLIAM SIMPSON, E. L, M. E. A. S. 



IT is necessary to premise that under the term " mud " I include 

 sun-dried bricks. When bricks have been burned in the fire, 

 the material becomes entirely changed and ceases to be mud, so I 

 exclude them from consideration in the present paper as a build- 

 ing material. Wet earth made into blocks and dried in the sun 

 differs in no way from a layer of the same laid on a wall.* Both 

 methods were used in the East, and often combined in the same 

 building. The reason for this is soon found out if you attempt 

 to raise a mud wall. A layer of two or three feet thick must be 

 allowed to dry and consolidate before another is placed on it, be- 

 cause the weight above would press out the soft material below, 

 and the whole would tumble down. In some localities a layer of 

 mud is put down at the commencement, and while that is drying 

 bricks are made to be placed above. 



It was during the cold season of 1884-'85, in traveling through 

 Persia at the time of the Afghan Boundary Commission, that the 



* Bricks of this kind, " when placed one upon another after being imperfectly dried, 

 combined, under the influence of the weather and their own weight, into one homogeneous 

 mass, so that the separate courses became undistinguishable. This latter fact has been 

 frequently noticed in Assyria, by those who had to cut through the thickness of walls in the 

 process of excavation." Perrot and Chipiez, A History of Art in Ancient Egypt, vol. i, 

 p. 113. 



