48 7 H. BURCHARTZ. 
steam and the dust from the sand being raised by the steam 
exhausterd; dry sand only is thrown against the specimen. 
The slide e allows the immediate stoppage of the sand 
stream. The test piece g is fixed in the frame f and is 
moved over the sand blast by turning the handle by means 
A new apparatus for testing building materials on abrasion. Scale 1 : 10. 
of a planet driving gear. Under the sample is placed a 
sheet iron templet with a round opening of 6 c/m.=(2°4 
inches) diameter, and the sand blast makes a recess in the 
material only on this area of 28 sq. c/m. = (4°34 sq. inches). 
This recess shows the quality and the characteristic quali- 
ties of the material, and the more or less homogeneity of 
