53 
CASE 15— Foreign building stones. Roofing slate. 
Specimens of slate from the Welsh quarries illustrate the 
manner in which blocks of slate are split or cleaved into a 
series of laminae or thin plates, which may be afterwards cut to 
uniform sizes and used for roofing. 
HALL 68 
CLAYS AND SANDS. 
Kaolin or Clay is the basis of most of the specimens shown 
in this room. 
CASE 1.— Sand and cement. A collection showing all 
stages in the manufacture of Portland cement. A collection 
showing varieties of sand adapted to different uses, such as mold- 
ing sand for molds for metal castings; pure sand for infusible 
furnace hearths and furnace bricks; sand for the manufacture 
of glass, etc. 
CASES 2 AND 4 .— Briquettes. These are miniature bricks 
made from a great variety of foreign and domestic clays and 
designed to illustrate the variety in color, density and other 
characters of bricks made from these clays. 
CASE 3. — Natural pigments used for paints. The greater 
number are ochres or' clays colored red, yellow or brown by 
oxides of iron and manganese. 
CASES 5, 6, 8 AND 12.— Brick clays. Brick clays are the 
common clays. Any clay that can be molded and will bake to 
brick without deforming or cracking may be used as a brick 
clay. Such clays are usually very impure. 
CASE 7. — Soils. A collection designed to illustrate the 
formation of soils from rocks — and to show the different kinds 
of soils and their compositions. 
CASE 9. — Fine clays. These include the porcelain and 
china clays, pipe and paper clays with fuller’s earth and other 
clays suited to special uses. 
CASE 10. Fire clays and objects made from them and 
designed to withstand intense heat. ^ _ 
CASE 11 .— Composition of clays. A collection des-gned to 
show what are the usual components of clays and what effect 
