20° ON THE ACTION OF TRANSPARENT BODIES 
81. Tartrate of Potash and Soda. 
This salt acts more powerfully upon green light than flint- 
glass, and does not appear to act very differently from crown- 
glass. 
82. Thyme, Oil of. 
This oil acts. less powerfully upon green light. than flint’ 
and crown glass, and oil of juniper, but more powerfully than: 
oil of cloves. 
83. Tolu, Balsam of. 
This balsam acts less powerfully upon the green rays than: 
oil of anise-seeds, oil of sassafras, and oil of lavender, and fint- 
glass, but more powerfully than oil of cassia and sulphuret of 
carbon. 
84. Topaz, Blue. 
This mineral acts more powerfully upon green light than: 
crown and flint glass, selenite, and Jeucite, but less powerfully 
than water and rock-erystal. 
85. Tourmaline. 
This mineral acts more powerfully upon green light than: 
crown and flint glass. 
86. Turpentine, Oil of: 
This oil acts more powerfully upon the green rays than oil 
of sassafras, oil of cloves, and Canada balsam, but less power- 
fully than crown and flint glass. ; 
87. Water: 
