Chemical Laboratory, University of Minnesota. 347 



Sample No. 4. — From Nos. 141 and 143 Lyndale Ave. 

 North, Minneapolis, Minn. 



Calcium sulphate — mainly. 

 Magnesium sulphate — trace. 

 Sodium sulphate — trace. 



Location — damp. 



Coating — medium 



Mortar — red. 



Backing — red brick, laid in red mortar. 



Sample No. 5. — From corner of 5th Ave. and 14th St. South, 

 Minneapolis, Minnesota. 



Calcium sulphate — mainly. 

 Magnesium sulphate — considerable. 

 Sodium sulphate — trace. 



Location — damp. 



Coating — thick. 



Mortar — red. 



Backing — red brick, laid in red mortar. 



Sample No. 6. — From Union Station, Minneapolis, Minn. 



Magnesium sulphate — mainly. 

 Sodium sulphate — trace. 



Location — damp. 



Coating — very thick. 



Mortar — red. 



Backing — yellow brick, laid in white mortar. 



Sample No. 7. — From a brick left exposed to the action of 

 the atmosphere for about six months. 



Magnesium sulphate — mainly. 

 Sodium sulphate — trace. 



Location — dry. 



Coating — very thin. 



May ^tli, t8qi. 



